<div id="docs-body">
 <div class="section">
  <div class="titlepage">
   <div>
    <div>
     <h3 class="title">
      <a name="server-system-variables">
      </a>
      7.1.8 Server System Variables
     </h3>
    </div>
   </div>
  </div>
  <a class="indexterm" name="idm46045278726128">
  </a>
  <a class="indexterm" name="idm46045278725056">
  </a>
  <a class="indexterm" name="idm46045278723568">
  </a>
  <p>
   The MySQL server maintains many system variables that affect its
      operation. Most system variables can be set at server startup
      using options on the command line or in an option file. Most of
      them can be changed dynamically at runtime using the
   <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
    <code class="literal">
     SET
    </code>
   </a>
   statement, which enables you to modify operation of the server
      without having to stop and restart it. Some variables are
      read-only, and their values are determined by the system
      environment, by how MySQL is installed on the system, or possibly
      by the options used to compile MySQL. Most system variables have a
      default value, but there are exceptions, including read-only
      variables. You can also use system variable values in expressions.
  </p>
  <p>
   Setting a global system variable runtime value normally requires
      the
   <a class="link" href="privileges-provided.html#priv_system-variables-admin">
    <code class="literal">
     SYSTEM_VARIABLES_ADMIN
    </code>
   </a>
   privilege (or the deprecated
   <a class="link" href="privileges-provided.html#priv_super">
    <code class="literal">
     SUPER
    </code>
   </a>
   privilege). Setting a session system runtime variable value
      normally requires no special privileges and can be done by any
      user, although there are exceptions. For more information, see
   <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
    Section 7.1.9.1, “System Variable Privileges”
   </a>
  </p>
  <p>
   There are several ways to see the names and values of system
      variables:
  </p>
  <div class="itemizedlist">
   <ul class="itemizedlist" style="list-style-type: disc; ">
    <li class="listitem">
     <p>
      To see the values that a server uses based on its compiled-in
          defaults and any option files that it reads, use this command:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa5921026"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqld <span class="token property">--verbose</span> <span class="token property">--help</span></code></pre>
     </div>
    </li>
    <li class="listitem">
     <p>
      To see the values that a server uses based only on its
          compiled-in defaults, ignoring the settings in any option
          files, use this command:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa43122592"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqld <span class="token property">--no-defaults</span> <span class="token property">--verbose</span> <span class="token property">--help</span></code></pre>
     </div>
    </li>
    <li class="listitem">
     <p>
      To see the current values used by a running server, use the
      <a class="link" href="show-variables.html" title="15.7.7.41 SHOW VARIABLES Statement">
       <code class="literal">
        SHOW VARIABLES
       </code>
      </a>
      statement or the
          Performance Schema system variable tables. See
      <a class="xref" href="performance-schema-system-variable-tables.html" title="29.12.14 Performance Schema System Variable Tables">
       Section 29.12.14, “Performance Schema System Variable Tables”
      </a>
      .
     </p>
    </li>
   </ul>
  </div>
  <p>
   This section provides a description of each system variable. For a
      system variable summary table, see
   <a class="xref" href="server-system-variable-reference.html" title="7.1.5 Server System Variable Reference">
    Section 7.1.5, “Server System Variable Reference”
   </a>
   . For more
      information about manipulation of system variables, see
   <a class="xref" href="using-system-variables.html" title="7.1.9 Using System Variables">
    Section 7.1.9, “Using System Variables”
   </a>
   .
  </p>
  <p>
   For additional system variable information, see these sections:
  </p>
  <div class="itemizedlist">
   <ul class="itemizedlist" style="list-style-type: disc; ">
    <li class="listitem">
     <p>
      <a class="xref" href="using-system-variables.html" title="7.1.9 Using System Variables">
       Section 7.1.9, “Using System Variables”
      </a>
      , discusses the syntax
          for setting and displaying system variable values.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a class="xref" href="dynamic-system-variables.html" title="7.1.9.2 Dynamic System Variables">
       Section 7.1.9.2, “Dynamic System Variables”
      </a>
      , lists the
          variables that can be set at runtime.
     </p>
    </li>
    <li class="listitem">
     <p>
      Information on tuning system variables can be found in
      <a class="xref" href="server-configuration.html" title="7.1.1 Configuring the Server">
       Section 7.1.1, “Configuring the Server”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a class="xref" href="innodb-parameters.html" title="17.14 InnoDB Startup Options and System Variables">
       Section 17.14, “InnoDB Startup Options and System Variables”
      </a>
      , lists
      <code class="literal">
       InnoDB
      </code>
      system variables.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a class="xref" href="mysql-cluster-options-variables.html#mysql-cluster-system-variables" title="25.4.3.9.2 NDB Cluster System Variables">
       Section 25.4.3.9.2, “NDB Cluster System Variables”
      </a>
      , lists system
          variables which are specific to NDB Cluster.
     </p>
    </li>
    <li class="listitem">
     <p>
      For information on server system variables specific to
          replication, see
      <a class="xref" href="replication-options.html" title="19.1.6 Replication and Binary Logging Options and Variables">
       Section 19.1.6, “Replication and Binary Logging Options and Variables”
      </a>
      .
     </p>
    </li>
   </ul>
  </div>
  <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
   <div class="admon-title">
    Note
   </div>
   <p>
    Some of the following variable descriptions refer to
    <span class="quote">
     “
     <span class="quote">
      enabling
     </span>
     ”
    </span>
    or
    <span class="quote">
     “
     <span class="quote">
      disabling
     </span>
     ”
    </span>
    a variable.
        These variables can be enabled with the
    <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
     <code class="literal">
      SET
     </code>
    </a>
    statement by setting them to
    <code class="literal">
     ON
    </code>
    or
    <code class="literal">
     1
    </code>
    , or disabled by setting them to
    <code class="literal">
     OFF
    </code>
    or
    <code class="literal">
     0
    </code>
    . Boolean
        variables can be set at startup to the values
    <code class="literal">
     ON
    </code>
    ,
    <code class="literal">
     TRUE
    </code>
    ,
    <code class="literal">
     OFF
    </code>
    , and
    <code class="literal">
     FALSE
    </code>
    (not
        case-sensitive), as well as
    <code class="literal">
     1
    </code>
    and
    <code class="literal">
     0
    </code>
    . See
    <a class="xref" href="option-modifiers.html" title="6.2.2.4 Program Option Modifiers">
     Section 6.2.2.4, “Program Option Modifiers”
    </a>
    .
   </p>
  </div>
  <p>
   Some system variables control the size of buffers or caches. For a
      given buffer, the server might need to allocate internal data
      structures. These structures typically are allocated from the
      total memory allocated to the buffer, and the amount of space
      required might be platform dependent. This means that when you
      assign a value to a system variable that controls a buffer size,
      the amount of space actually available might differ from the value
      assigned. In some cases, the amount might be less than the value
      assigned. It is also possible that the server adjusts a value
      upward. For example, if you assign a value of 0 to a variable for
      which the minimal value is 1024, the server sets the value to
      1024.
  </p>
  <p>
   Values for buffer sizes, lengths, and stack sizes are given in
      bytes unless otherwise specified.
  </p>
  <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
   <div class="admon-title">
    <a name="system-variables-block-size">
    </a>
    Note
   </div>
   <p>
    Some system variable descriptions include a block size, in which
        case a value that is not an integer multiple of the stated block
        size is rounded down to the next lower multiple of the block
        size before being stored by the server, that is to
    <a class="link" href="mathematical-functions.html#function_floor">
     <code class="literal">
      FLOOR(
      <em class="replaceable">
       <code>
        value
       </code>
      </em>
      )
     </code>
    </a>
    <code class="literal">
     *
     <em class="replaceable">
      <code>
       block_size
      </code>
     </em>
    </code>
    .
   </p>
   <p>
    <span class="emphasis">
     <em>
      Example
     </em>
    </span>
    : Suppose that the block size for a
        given variable is given as 4096, and you set the value of the
        variable to 100000 (we assume that the variable's maximum
        value is greater than this number). Since 100000 / 4096 =
        24.4140625, the server automatically lowers the value to 98304
        (24 * 4096) before storing it.
   </p>
   <p>
    In some cases, the stated maximum for a variable is the maximum
        allowed by the MySQL parser, but is not an exact multiple of the
        block size. In such cases, the effective maximum is the next
        lower multiple of the block size.
   </p>
   <p>
    <span class="emphasis">
     <em>
      Example
     </em>
    </span>
    : A system variable's maxmum
        value is shown as 4294967295 (2
    <sup>
     32
    </sup>
    -1),
        and its block size is 1024. 4294967295 / 1024 =
        4194303.9990234375, so if you set this variable to its stated
        maximum, the value actually stored is 4194303 * 1024 =
        4294966272.
   </p>
  </div>
  <p>
   Some system variables take file name values. Unless otherwise
      specified, the default file location is the data directory if the
      value is a relative path name. To specify the location explicitly,
      use an absolute path name. Suppose that the data directory is
   <code class="filename">
    /var/mysql/data
   </code>
   . If a file-valued variable is
      given as a relative path name, it is located under
   <code class="filename">
    /var/mysql/data
   </code>
   . If the value is an absolute
      path name, its location is as given by the path name.
  </p>
  <div class="itemizedlist">
   <ul class="itemizedlist" style="list-style-type: disc; ">
    <li class="listitem">
     <p>
      <a name="sysvar_activate_all_roles_on_login">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_activate_all_roles_on_login">
       <code class="literal">
        activate_all_roles_on_login
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278669888">
     </a>
     <a class="indexterm" name="idm46045278668784">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for activate_all_roles_on_login">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --activate-all-roles-on-login[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_activate_all_roles_on_login">
            activate_all_roles_on_login
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether to enable automatic activation of all granted roles
          when users log in to the server:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         If
         <a class="link" href="server-system-variables.html#sysvar_activate_all_roles_on_login">
          <code class="literal">
           activate_all_roles_on_login
          </code>
         </a>
         is enabled, the server activates all roles granted to each
              account at login time. This takes precedence over default
              roles specified with
         <a class="link" href="set-default-role.html" title="15.7.1.9 SET DEFAULT ROLE Statement">
          <code class="literal">
           SET DEFAULT
              ROLE
          </code>
         </a>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         If
         <a class="link" href="server-system-variables.html#sysvar_activate_all_roles_on_login">
          <code class="literal">
           activate_all_roles_on_login
          </code>
         </a>
         is disabled, the server activates the default roles
              specified with
         <a class="link" href="set-default-role.html" title="15.7.1.9 SET DEFAULT ROLE Statement">
          <code class="literal">
           SET DEFAULT
              ROLE
          </code>
         </a>
         , if any, at login time.
        </p>
       </li>
      </ul>
     </div>
     <p>
      Granted roles include those granted explicitly to the user and
          those named in the
      <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
       <code class="literal">
        mandatory_roles
       </code>
      </a>
      system
          variable value.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_activate_all_roles_on_login">
       <code class="literal">
        activate_all_roles_on_login
       </code>
      </a>
      applies only at login time, and at the beginning of execution
          for stored programs and views that execute in definer context.
          To change the active roles within a session, use
      <a class="link" href="set-role.html" title="15.7.1.11 SET ROLE Statement">
       <code class="literal">
        SET ROLE
       </code>
      </a>
      . To change the active
          roles for a stored program, the program body should execute
      <a class="link" href="set-role.html" title="15.7.1.11 SET ROLE Statement">
       <code class="literal">
        SET ROLE
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_admin_address">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_admin_address">
       <code class="literal">
        admin_address
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278630368">
     </a>
     <a class="indexterm" name="idm46045278629280">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for admin_address">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --admin-address=addr
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_admin_address">
            admin_address
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The IP address on which to listen for TCP/IP connections on
          the administrative network interface (see
      <a class="xref" href="connection-interfaces.html" title="7.1.12.1 Connection Interfaces">
       Section 7.1.12.1, “Connection Interfaces”
      </a>
      ). There is no default
      <a class="link" href="server-system-variables.html#sysvar_admin_address">
       <code class="literal">
        admin_address
       </code>
      </a>
      value. If this
          variable is not specified at startup, the server maintains no
          administrative interface. The server also has a
      <a class="link" href="server-system-variables.html#sysvar_bind_address">
       <code class="literal">
        bind_address
       </code>
      </a>
      system variable
          for configuring regular (nonadministrative) client TCP/IP
          connections. See
      <a class="xref" href="connection-interfaces.html" title="7.1.12.1 Connection Interfaces">
       Section 7.1.12.1, “Connection Interfaces”
      </a>
      .
     </p>
     <p>
      If
      <a class="link" href="server-system-variables.html#sysvar_admin_address">
       <code class="literal">
        admin_address
       </code>
      </a>
      is
          specified, its value must satisfy these requirements:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         The value must be a single IPv4 address, IPv6 address, or
              host name.
        </p>
       </li>
       <li class="listitem">
        <p>
         The value cannot specify a wildcard address format
              (
         <code class="literal">
          *
         </code>
         ,
         <code class="literal">
          0.0.0.0
         </code>
         , or
         <code class="literal">
          ::
         </code>
         ).
        </p>
       </li>
       <li class="listitem">
        <p>
         The value may include a network namespace specifier.
        </p>
       </li>
      </ul>
     </div>
     <p>
      An IP address can be specified as an IPv4 or IPv6 address. If
          the value is a host name, the server resolves the name to an
          IP address and binds to that address. If a host name resolves
          to multiple IP addresses, the server uses the first IPv4
          address if there are any, or the first IPv6 address otherwise.
     </p>
     <p>
      The server treats different types of addresses as follows:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         If the address is an IPv4-mapped address, the server
              accepts TCP/IP connections for that address, in either
              IPv4 or IPv6 format. For example, if the server is bound
              to
         <code class="literal">
          ::ffff:127.0.0.1
         </code>
         , clients can
              connect using
         <code class="option">
          --host=127.0.0.1
         </code>
         or
         <code class="option">
          --host=::ffff:127.0.0.1
         </code>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         If the address is a
         <span class="quote">
          “
          <span class="quote">
           regular
          </span>
          ”
         </span>
         IPv4 or IPv6
              address (such as
         <code class="literal">
          127.0.0.1
         </code>
         or
         <code class="literal">
          ::1
         </code>
         ), the server accepts TCP/IP
              connections only for that IPv4 or IPv6 address.
        </p>
       </li>
      </ul>
     </div>
     <p>
      These rules apply to specifying a network namespace for an
          address:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         A network namespace can be specified for an IP address or
              a host name.
        </p>
       </li>
       <li class="listitem">
        <p>
         A network namespace cannot be specified for a wildcard IP
              address.
        </p>
       </li>
       <li class="listitem">
        <p>
         For a given address, the network namespace is optional. If
              given, it must be specified as a
         <code class="literal">
          /
          <em class="replaceable">
           <code>
            ns
           </code>
          </em>
         </code>
         suffix
              immediately following the address.
        </p>
       </li>
       <li class="listitem">
        <p>
         An address with no
         <code class="literal">
          /
          <em class="replaceable">
           <code>
            ns
           </code>
          </em>
         </code>
         suffix
              uses the host system global namespace. The global
              namespace is therefore the default.
        </p>
       </li>
       <li class="listitem">
        <p>
         An address with a
         <code class="literal">
          /
          <em class="replaceable">
           <code>
            ns
           </code>
          </em>
         </code>
         suffix
              uses the namespace named
         <em class="replaceable">
          <code>
           ns
          </code>
         </em>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         The host system must support network namespaces and each
              named namespace must previously have been set up. Naming a
              nonexistent namespace produces an error.
        </p>
       </li>
      </ul>
     </div>
     <p>
      For additional information about network namespaces, see
      <a class="xref" href="network-namespace-support.html" title="7.1.14 Network Namespace Support">
       Section 7.1.14, “Network Namespace Support”
      </a>
      .
     </p>
     <p>
      If binding to the address fails, the server produces an error
          and does not start.
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_admin_address">
       <code class="literal">
        admin_address
       </code>
      </a>
      system
          variable is similar to the
      <a class="link" href="server-system-variables.html#sysvar_bind_address">
       <code class="literal">
        bind_address
       </code>
      </a>
      system variable
          that binds the server to an address for ordinary client
          connections, but with these differences:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <a class="link" href="server-system-variables.html#sysvar_bind_address">
          <code class="literal">
           bind_address
          </code>
         </a>
         permits
              multiple addresses.
         <a class="link" href="server-system-variables.html#sysvar_admin_address">
          <code class="literal">
           admin_address
          </code>
         </a>
         permits a
              single address.
        </p>
       </li>
       <li class="listitem">
        <p>
         <a class="link" href="server-system-variables.html#sysvar_bind_address">
          <code class="literal">
           bind_address
          </code>
         </a>
         permits
              wildcard addresses.
         <a class="link" href="server-system-variables.html#sysvar_admin_address">
          <code class="literal">
           admin_address
          </code>
         </a>
         does not.
        </p>
       </li>
      </ul>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_admin_port">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_admin_port">
       <code class="literal">
        admin_port
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278567664">
     </a>
     <a class="indexterm" name="idm46045278566576">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for admin_port">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --admin-port=port_num
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_admin_port">
            admin_port
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           33062
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           65535
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The TCP/IP port number to use for connections on the
          administrative network interface (see
      <a class="xref" href="connection-interfaces.html" title="7.1.12.1 Connection Interfaces">
       Section 7.1.12.1, “Connection Interfaces”
      </a>
      ). Setting this
          variable to 0 causes the default value to be used.
     </p>
     <p>
      Setting
      <a class="link" href="server-system-variables.html#sysvar_admin_port">
       <code class="literal">
        admin_port
       </code>
      </a>
      has no
          effect if
      <a class="link" href="server-system-variables.html#sysvar_admin_address">
       <code class="literal">
        admin_address
       </code>
      </a>
      is
          not specified because in that case the server maintains no
          administrative network interface.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_admin_ssl_ca">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_ca">
       <code class="literal">
        admin_ssl_ca
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278533424">
     </a>
     <a class="indexterm" name="idm46045278532336">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for admin_ssl_ca">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --admin-ssl-ca=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_admin_ssl_ca">
            admin_ssl_ca
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_ca">
       <code class="literal">
        admin_ssl_ca
       </code>
      </a>
      system
          variable is like
      <a class="link" href="server-system-variables.html#sysvar_ssl_ca">
       <code class="literal">
        ssl_ca
       </code>
      </a>
      ,
          except that it applies to the administrative connection
          interface rather than the main connection interface. For
          information about configuring encryption support for the
          administrative interface, see
      <a class="xref" href="administrative-connection-interface.html#administrative-interface-encrypted-connections" title="Administrative Interface Support for Encrypted Connections">
       Administrative Interface Support for Encrypted Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_admin_ssl_capath">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_capath">
       <code class="literal">
        admin_ssl_capath
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278504304">
     </a>
     <a class="indexterm" name="idm46045278503216">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for admin_ssl_capath">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --admin-ssl-capath=dir_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_admin_ssl_capath">
            admin_ssl_capath
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Directory name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_capath">
       <code class="literal">
        admin_ssl_capath
       </code>
      </a>
      system
          variable is like
      <a class="link" href="server-system-variables.html#sysvar_ssl_capath">
       <code class="literal">
        ssl_capath
       </code>
      </a>
      ,
          except that it applies to the administrative connection
          interface rather than the main connection interface. For
          information about configuring encryption support for the
          administrative interface, see
      <a class="xref" href="administrative-connection-interface.html#administrative-interface-encrypted-connections" title="Administrative Interface Support for Encrypted Connections">
       Administrative Interface Support for Encrypted Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_admin_ssl_cert">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_cert">
       <code class="literal">
        admin_ssl_cert
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278475312">
     </a>
     <a class="indexterm" name="idm46045278474224">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for admin_ssl_cert">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --admin-ssl-cert=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_admin_ssl_cert">
            admin_ssl_cert
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_cert">
       <code class="literal">
        admin_ssl_cert
       </code>
      </a>
      system
          variable is like
      <a class="link" href="server-system-variables.html#sysvar_ssl_cert">
       <code class="literal">
        ssl_cert
       </code>
      </a>
      ,
          except that it applies to the administrative connection
          interface rather than the main connection interface. For
          information about configuring encryption support for the
          administrative interface, see
      <a class="xref" href="administrative-connection-interface.html#administrative-interface-encrypted-connections" title="Administrative Interface Support for Encrypted Connections">
       Administrative Interface Support for Encrypted Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_admin_ssl_cipher">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_cipher">
       <code class="literal">
        admin_ssl_cipher
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278446384">
     </a>
     <a class="indexterm" name="idm46045278445296">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for admin_ssl_cipher">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --admin-ssl-cipher=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_admin_ssl_cipher">
            admin_ssl_cipher
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_cipher">
       <code class="literal">
        admin_ssl_cipher
       </code>
      </a>
      system
          variable is like
      <a class="link" href="server-system-variables.html#sysvar_ssl_cipher">
       <code class="literal">
        ssl_cipher
       </code>
      </a>
      ,
          except that it applies to the administrative connection
          interface rather than the main connection interface. For
          information about configuring encryption support for the
          administrative interface, see
      <a class="xref" href="administrative-connection-interface.html#administrative-interface-encrypted-connections" title="Administrative Interface Support for Encrypted Connections">
       Administrative Interface Support for Encrypted Connections
      </a>
      .
     </p>
     <p>
      The list specified by this variable may include any of the
          following values:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-ECDSA-AES128-GCM-SHA256
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-ECDSA-AES256-GCM-SHA384
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-RSA-AES128-GCM-SHA256
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-RSA-AES256-GCM-SHA384
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-ECDSA-CHACHA20-POLY1305
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-RSA-CHACHA20-POLY1305
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-ECDSA-AES256-CCM
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-ECDSA-AES128-CCM
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          DHE-RSA-AES128-GCM-SHA256
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          DHE-RSA-AES256-GCM-SHA384
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          DHE-RSA-AES256-CCM
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          DHE-RSA-AES128-CCM
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          DHE-RSA-CHACHA20-POLY1305
         </code>
        </p>
       </li>
      </ul>
     </div>
     <p>
      Trying to include any values in the cipher list that are not
          shown here when setting this variable raises an error
          (
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_blocked_cipher" target="_top">
       <code class="literal">
        ER_BLOCKED_CIPHER
       </code>
      </a>
      ).
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_admin_ssl_crl">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_crl">
       <code class="literal">
        admin_ssl_crl
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278395760">
     </a>
     <a class="indexterm" name="idm46045278394672">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for admin_ssl_crl">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --admin-ssl-crl=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_admin_ssl_crl">
            admin_ssl_crl
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_crl">
       <code class="literal">
        admin_ssl_crl
       </code>
      </a>
      system
          variable is like
      <a class="link" href="server-system-variables.html#sysvar_ssl_crl">
       <code class="literal">
        ssl_crl
       </code>
      </a>
      ,
          except that it applies to the administrative connection
          interface rather than the main connection interface. For
          information about configuring encryption support for the
          administrative interface, see
      <a class="xref" href="administrative-connection-interface.html#administrative-interface-encrypted-connections" title="Administrative Interface Support for Encrypted Connections">
       Administrative Interface Support for Encrypted Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_admin_ssl_crlpath">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_crlpath">
       <code class="literal">
        admin_ssl_crlpath
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278366720">
     </a>
     <a class="indexterm" name="idm46045278365680">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for admin_ssl_crlpath">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --admin-ssl-crlpath=dir_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_admin_ssl_crlpath">
            admin_ssl_crlpath
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Directory name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_crlpath">
       <code class="literal">
        admin_ssl_crlpath
       </code>
      </a>
      system
          variable is like
      <a class="link" href="server-system-variables.html#sysvar_ssl_crlpath">
       <code class="literal">
        ssl_crlpath
       </code>
      </a>
      ,
          except that it applies to the administrative connection
          interface rather than the main connection interface. For
          information about configuring encryption support for the
          administrative interface, see
      <a class="xref" href="administrative-connection-interface.html#administrative-interface-encrypted-connections" title="Administrative Interface Support for Encrypted Connections">
       Administrative Interface Support for Encrypted Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_admin_ssl_key">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_key">
       <code class="literal">
        admin_ssl_key
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278337776">
     </a>
     <a class="indexterm" name="idm46045278336688">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for admin_ssl_key">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --admin-ssl-key=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_admin_ssl_key">
            admin_ssl_key
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_admin_ssl_key">
       <code class="literal">
        admin_ssl_key
       </code>
      </a>
      system
          variable is like
      <a class="link" href="server-system-variables.html#sysvar_ssl_key">
       <code class="literal">
        ssl_key
       </code>
      </a>
      ,
          except that it applies to the administrative connection
          interface rather than the main connection interface. For
          information about configuring encryption support for the
          administrative interface, see
      <a class="xref" href="administrative-connection-interface.html#administrative-interface-encrypted-connections" title="Administrative Interface Support for Encrypted Connections">
       Administrative Interface Support for Encrypted Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_admin_tls_ciphersuites">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_admin_tls_ciphersuites">
       <code class="literal">
        admin_tls_ciphersuites
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278308736">
     </a>
     <a class="indexterm" name="idm46045278307696">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for admin_tls_ciphersuites">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --admin-tls-ciphersuites=ciphersuite_list
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_admin_tls_ciphersuites">
            admin_tls_ciphersuites
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_admin_tls_ciphersuites">
       <code class="literal">
        admin_tls_ciphersuites
       </code>
      </a>
      system variable is like
      <a class="link" href="server-system-variables.html#sysvar_tls_ciphersuites">
       <code class="literal">
        tls_ciphersuites
       </code>
      </a>
      , except that
          it applies to the administrative connection interface rather
          than the main connection interface. For information about
          configuring encryption support for the administrative
          interface, see
      <a class="xref" href="administrative-connection-interface.html#administrative-interface-encrypted-connections" title="Administrative Interface Support for Encrypted Connections">
       Administrative Interface Support for Encrypted Connections
      </a>
      .
     </p>
     <p>
      The value is a list of zero or more colon-separated
          ciphersuite names from among those listed here:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          TLS_AES_128_GCM_SHA256
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          TLS_AES_256_GCM_SHA384
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          TLS_CHACHA20_POLY1305_SHA256
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          TLS_AES_128_CCM_SHA256
         </code>
        </p>
       </li>
      </ul>
     </div>
     <p>
      Trying to include any values in the cipher list that are not
          shown here when setting this variable raises an error
          (
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_blocked_cipher" target="_top">
       <code class="literal">
        ER_BLOCKED_CIPHER
       </code>
      </a>
      ).
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_admin_tls_version">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_admin_tls_version">
       <code class="literal">
        admin_tls_version
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278271088">
     </a>
     <a class="indexterm" name="idm46045278270048">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for admin_tls_version">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --admin-tls-version=protocol_list
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_admin_tls_version">
            admin_tls_version
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           TLSv1.2,TLSv1.3
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_admin_tls_version">
       <code class="literal">
        admin_tls_version
       </code>
      </a>
      system
          variable is like
      <a class="link" href="server-system-variables.html#sysvar_tls_version">
       <code class="literal">
        tls_version
       </code>
      </a>
      ,
          except that it applies to the administrative connection
          interface rather than the main connection interface. For
          information about configuring encryption support for the
          administrative interface, see
      <a class="xref" href="administrative-connection-interface.html#administrative-interface-encrypted-connections" title="Administrative Interface Support for Encrypted Connections">
       Administrative Interface Support for Encrypted Connections
      </a>
      .
     </p>
     <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Important
      </div>
      <div class="itemizedlist">
       <ul class="itemizedlist" style="list-style-type: circle; ">
        <li class="listitem">
         <p>
          MySQL 8.4 does not support the TLSv1 and
                TLSv1.1 connection protocols. See
          <a class="xref" href="encrypted-connection-protocols-ciphers.html#encrypted-connection-deprecated-protocols" title="Removal of Support for the TLSv1 and TLSv1.1 Protocols">
           Removal of Support for the TLSv1 and TLSv1.1 Protocols
          </a>
          for more information.
         </p>
        </li>
        <li class="listitem">
         <p>
          MuySQL 8.4 supports the TLSv1.3 protocol,
                provided that the MySQL server was compiled using
                OpenSSL 1.1.1 or newer. The server checks the version of
                OpenSSL at startup, and if it is older than 1.1.1,
                TLSv1.3 is removed from the default value for the system
                variable. In that case, the default is
          <code class="literal">
           TLSv1.2
          </code>
          .
         </p>
        </li>
       </ul>
      </div>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_authentication_policy">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_authentication_policy">
       <code class="literal">
        authentication_policy
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278237664">
     </a>
     <a class="indexterm" name="idm46045278236624">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for authentication_policy">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --authentication-policy=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_authentication_policy">
            authentication_policy
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           *,,
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable is used to administer multifactor authentication
          (MFA) capabilities. For
      <a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
       <code class="literal">
        CREATE
          USER
       </code>
      </a>
      and
      <a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
       <code class="literal">
        ALTER USER
       </code>
      </a>
      statements used to manage MySQL account definitions, it
          determines what authentication factor or factors may be
          specified, where
      <span class="quote">
       “
       <span class="quote">
        factor
       </span>
       ”
      </span>
      corresponds to an
          authentication method or plugin associated with an account.
      <code class="literal">
       authentication_policy
      </code>
      determines the
          following aspects of multifactor authentication:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         The number of authentication factors.
        </p>
       </li>
       <li class="listitem">
        <p>
         The plugins (or methods) permitted for each factor.
        </p>
       </li>
       <li class="listitem">
        <p>
         The default authentication plugin for authentication
              specifications that do not name a plugin explicitly.
        </p>
       </li>
      </ul>
     </div>
     <p>
      Because
      <a class="link" href="server-system-variables.html#sysvar_authentication_policy">
       <code class="literal">
        authentication_policy
       </code>
      </a>
      applies only when accounts are created or altered, changes to
          its value have no effect on existing user accounts.
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       Although the
       <a class="link" href="server-system-variables.html#sysvar_authentication_policy">
        <code class="literal">
         authentication_policy
        </code>
       </a>
       system variable places certain constraints on the
            authentication-related clauses of
       <a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
        <code class="literal">
         CREATE USER
        </code>
       </a>
       and
       <a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
        <code class="literal">
         ALTER USER
        </code>
       </a>
       statements, a user
            who has the
       <a class="link" href="privileges-provided.html#priv_authentication-policy-admin">
        <code class="literal">
         AUTHENTICATION_POLICY_ADMIN
        </code>
       </a>
       privilege is not subject to these constraints. (A warning
            does occur for statements that otherwise would not be
            permitted.)
      </p>
     </div>
     <p>
      The value of
      <a class="link" href="server-system-variables.html#sysvar_authentication_policy">
       <code class="literal">
        authentication_policy
       </code>
      </a>
      is a
          list of 1, 2, or 3 comma-separated elements, each
          corresponding to an authentication factor and each being of
          one of the forms listed here, with their meanings:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <span class="emphasis">
          <em>
           empty
          </em>
         </span>
        </p>
        <p>
         The authentication factor is optional; any authentication
              plugin may be used.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          *
         </code>
        </p>
        <p>
         The authentication factor is required; any authentication
              plugin may be used.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          <em class="replaceable">
           <code>
            plugin_name
           </code>
          </em>
         </code>
        </p>
        <p>
         The authentication factor is required; this factor must be
         <em class="replaceable">
          <code>
           plugin_name
          </code>
         </em>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          *:
          <em class="replaceable">
           <code>
            plugin_name
           </code>
          </em>
         </code>
        </p>
        <p>
         The authentication factor is required;
         <code class="literal">
          plugin_name
         </code>
         is the default, but another
              authentication plugin may be used.
        </p>
       </li>
      </ul>
     </div>
     <p>
      In each case, an element may be surrounded by whitespace
          characters. The entire list must be enclosed in single quotes.
     </p>
     <p>
      <code class="literal">
       authentication_policy
      </code>
      must contain at least
          one nonempty factor, and any empty factors must come at the
          end of the list, following any nonempty factors. This means
          that
      <code class="literal">
       ',,'
      </code>
      is not permitted because this
          signifies that all factors are optional. Every account must
          have at least one authentication factor.
     </p>
     <p>
      The default value of
      <a class="link" href="server-system-variables.html#sysvar_authentication_policy">
       <code class="literal">
        authentication_policy
       </code>
      </a>
      is
      <code class="literal">
       '*,,'
      </code>
      . This means that factor 1 is required
          in account definitions and can use any authentication plugin
          (with
      <code class="literal">
       caching_sha2_password
      </code>
      being the
          default), and that factors 2 and 3 are optional and each can
          use any authentication plugin.
     </p>
     <p>
      If
      <code class="literal">
       authentication_policy
      </code>
      does not specify a
          default plugin for the first factor, the default plugin for
          this factor is
      <code class="literal">
       caching_sha2_password
      </code>
      ,
          although another plugin may be used.
     </p>
     <p>
      The following table shows some possible values for
      <a class="link" href="server-system-variables.html#sysvar_authentication_policy">
       <code class="literal">
        authentication_policy
       </code>
      </a>
      and the
          policy that each establishes for creating or altering
          accounts.
     </p>
     <div class="table">
      <a name="idm46045278178080">
      </a>
      <p class="title">
       <b>
        Table 7.4 Example authentication_policy Values
       </b>
      </p>
      <div class="table-contents">
       <table summary="Example authentication_policy values and their meanings.">
        <colgroup>
         <col style="width: 30%"/>
         <col style="width: 70%"/>
        </colgroup>
        <thead>
         <tr>
          <th>
           authentication_policy
          </th>
          <th>
           Policy
          </th>
         </tr>
        </thead>
        <tbody>
         <tr>
          <td>
           <code class="literal">
            '*'
           </code>
          </td>
          <td>
           One factor only, which uses
           <code class="literal">
            caching_sha2_password
           </code>
           ,
                although another plugin may be used.
          </td>
         </tr>
         <tr>
          <td>
           <code class="literal">
            '*,*'
           </code>
          </td>
          <td>
           Two factors only; the first factor uses
           <code class="literal">
            caching_sha2_password
           </code>
           by default,
                although another plugin may be used; the second may use
                any plugin.
          </td>
         </tr>
         <tr>
          <td>
           <code class="literal">
            '*,*,*'
           </code>
          </td>
          <td>
           Three factors only, where the first factor uses
           <code class="literal">
            caching_sha2_password
           </code>
           by default,
                although another plugin may be used; the second and
                third factors may use any plugins.
          </td>
         </tr>
         <tr>
          <td>
           <code class="literal">
            '*,'
           </code>
          </td>
          <td>
           One or two factors, where the first factor uses
           <code class="literal">
            caching_sha2_password
           </code>
           by default,
                although another plugin may be used; the second factor
                is optional and may use any plugin.
          </td>
         </tr>
         <tr>
          <td>
           <code class="literal">
            '*,,'
           </code>
          </td>
          <td>
           One, two, or three factors, where the first factor uses
           <code class="literal">
            caching_sha2_password
           </code>
           by default,
                although another plugin may be used; the second factor
                and third factors are optional and may use any plugins.
          </td>
         </tr>
         <tr>
          <td>
           <code class="literal">
            '*,*,'
           </code>
          </td>
          <td>
           Two or three factors, where the first factor uses
           <code class="literal">
            caching_sha2_password
           </code>
           by default,
                although another plugin may be used; the second factor
                is required and the third factor is optional; the second
                and third factors may use any plugins.
          </td>
         </tr>
         <tr>
          <td>
           <code class="literal">
            '*,
            <em class="replaceable">
             <code>
              auth_plugin
             </code>
            </em>
            '
           </code>
          </td>
          <td>
           Two factors, where the first factor uses
           <code class="literal">
            caching_sha2_password
           </code>
           by default,
                although another plugin may be used; the second factor
                must be the named plugin.
          </td>
         </tr>
         <tr>
          <td>
           <code class="literal">
            '
            <em class="replaceable">
             <code>
              auth_plugin
             </code>
            </em>
            ,*,'
           </code>
          </td>
          <td>
           Two or three factors, where the first factor must be the named plugin;
                the second factor is required but may use any plugin;
                the third factor is optional and may use any plugin.
          </td>
         </tr>
         <tr>
          <td>
           <code class="literal">
            '*,*:
            <em class="replaceable">
             <code>
              auth_plugin
             </code>
            </em>
            '
           </code>
          </td>
          <td>
           Two factors, where the first factor uses
           <code class="literal">
            caching_sha2_password
           </code>
           by default,
                although another plugin may be used; the second factor
                is required and uses the named plugin, but another
                plugin may be used.
          </td>
         </tr>
         <tr>
          <td>
           <code class="literal">
            '
            <em class="replaceable">
             <code>
              auth_plugin
             </code>
            </em>
            ,'
           </code>
          </td>
          <td>
           One or two factors, where the first factor must be the named plugin; the
                second factor is optional and may use any plugin.
          </td>
         </tr>
         <tr>
          <td>
           <code class="literal">
            '*:
            <em class="replaceable">
             <code>
              auth_plugin
             </code>
            </em>
            ,*,'
           </code>
          </td>
          <td>
           Two or three factors, where the first factor must be the named plugin;
                the second factor is required and may use any plugin,
                and the third factor is optional and may use any plugin.
          </td>
         </tr>
         <tr>
          <td>
           <code class="literal">
            '
            <em class="replaceable">
             <code>
              auth_plugin
             </code>
            </em>
            ,
            <em class="replaceable">
             <code>
              auth_plugin
             </code>
            </em>
            ,
            <em class="replaceable">
             <code>
              auth_plugin
             </code>
            </em>
            '
           </code>
          </td>
          <td>
           Three factors, where all three factors must use the named plugins.
          </td>
         </tr>
        </tbody>
       </table>
      </div>
      <div class="table-contents">
       <table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 431px; width: 709px;">
        <thead>
         <tr>
          <th style="width: 300.234px;">
           authentication_policy
          </th>
          <th style="width: 407.766px;">
           Policy
          </th>
         </tr>
        </thead>
       </table>
      </div>
     </div>
     <br class="table-break"/>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_authentication_windows_log_level">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_authentication_windows_log_level">
       <code class="literal">
        authentication_windows_log_level
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278128128">
     </a>
     <a class="indexterm" name="idm46045278127024">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for authentication_windows_log_level">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --authentication-windows-log-level=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_authentication_windows_log_level">
            authentication_windows_log_level
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           2
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable is available only if the
      <code class="literal">
       authentication_windows
      </code>
      Windows
          authentication plugin is enabled and debugging code is
          enabled. See
      <a class="xref" href="windows-pluggable-authentication.html" title="8.4.1.6 Windows Pluggable Authentication">
       Section 8.4.1.6, “Windows Pluggable Authentication”
      </a>
      .
     </p>
     <p>
      This variable sets the logging level for the Windows
          authentication plugin. The following table shows the permitted
          values.
     </p>
     <div class="informaltable">
      <table summary="Permitted values for the authentication_windows system variable.">
       <colgroup>
        <col style="width: 10%"/>
        <col style="width: 75%"/>
       </colgroup>
       <thead>
        <tr>
         <th>
          Value
         </th>
         <th>
          Description
         </th>
        </tr>
       </thead>
       <tbody>
        <tr>
         <td>
          0
         </td>
         <td>
          No logging
         </td>
        </tr>
        <tr>
         <td>
          1
         </td>
         <td>
          Log only error messages
         </td>
        </tr>
        <tr>
         <td>
          2
         </td>
         <td>
          Log level 1 messages and warning messages
         </td>
        </tr>
        <tr>
         <td>
          3
         </td>
         <td>
          Log level 2 messages and information notes
         </td>
        </tr>
        <tr>
         <td>
          4
         </td>
         <td>
          Log level 3 messages and debug messages
         </td>
        </tr>
       </tbody>
      </table>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_authentication_windows_use_principal_name">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_authentication_windows_use_principal_name">
       <code class="literal">
        authentication_windows_use_principal_name
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278079248">
     </a>
     <a class="indexterm" name="idm46045278078128">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for authentication_windows_use_principal_name">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --authentication-windows-use-principal-name[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_authentication_windows_use_principal_name">
            authentication_windows_use_principal_name
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable is available only if the
      <code class="literal">
       authentication_windows
      </code>
      Windows
          authentication plugin is enabled. See
      <a class="xref" href="windows-pluggable-authentication.html" title="8.4.1.6 Windows Pluggable Authentication">
       Section 8.4.1.6, “Windows Pluggable Authentication”
      </a>
      .
     </p>
     <p>
      A client that authenticates using the
      <code class="literal">
       InitSecurityContext()
      </code>
      function should
          provide a string identifying the service to which it connects
          (
      <em class="replaceable">
       <code>
        targetName
       </code>
      </em>
      ). MySQL uses the
          principal name (UPN) of the account under which the server is
          running. The UPN has the form
      <code class="literal">
       <em class="replaceable">
        <code>
         user_id
        </code>
       </em>
       @
       <em class="replaceable">
        <code>
         computer_name
        </code>
       </em>
      </code>
      and need not be registered anywhere to be used. This UPN is
          sent by the server at the beginning of authentication
          handshake.
     </p>
     <p>
      This variable controls whether the server sends the UPN in the
          initial challenge. By default, the variable is enabled. For
          security reasons, it can be disabled to avoid sending the
          server's account name to a client as cleartext. If the
          variable is disabled, the server always sends a
      <code class="literal">
       0x00
      </code>
      byte in the first challenge, the
          client does not specify
      <em class="replaceable">
       <code>
        targetName
       </code>
      </em>
      ,
          and as a result, NTLM authentication is used.
     </p>
     <p>
      If the server fails to obtain its UPN (which happens primarily
          in environments that do not support Kerberos authentication),
          the UPN is not sent by the server and NTLM authentication is
          used.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_autocommit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_autocommit">
       <code class="literal">
        autocommit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278046176">
     </a>
     <a class="indexterm" name="idm46045278045088">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for autocommit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --autocommit[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_autocommit">
            autocommit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The autocommit mode. If set to 1, all changes to a table take
          effect immediately. If set to 0, you must use
      <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
       <code class="literal">
        COMMIT
       </code>
      </a>
      to accept a transaction
          or
      <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
       <code class="literal">
        ROLLBACK
       </code>
      </a>
      to cancel it. If
      <a class="link" href="server-system-variables.html#sysvar_autocommit">
       <code class="literal">
        autocommit
       </code>
      </a>
      is 0 and you change it to 1, MySQL performs an automatic
      <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
       <code class="literal">
        COMMIT
       </code>
      </a>
      of any open transaction.
          Another way to begin a transaction is to use a
      <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
       <code class="literal">
        START
          TRANSACTION
       </code>
      </a>
      or
      <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
       <code class="literal">
        BEGIN
       </code>
      </a>
      statement. See
      <a class="xref" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
       Section 15.3.1, “START TRANSACTION, COMMIT, and ROLLBACK Statements”
      </a>
      .
     </p>
     <p>
      By default, client connections begin with
      <a class="link" href="server-system-variables.html#sysvar_autocommit">
       <code class="literal">
        autocommit
       </code>
      </a>
      set to 1. To cause
          clients to begin with a default of 0, set the global
      <a class="link" href="server-system-variables.html#sysvar_autocommit">
       <code class="literal">
        autocommit
       </code>
      </a>
      value by starting
          the server with the
      <a class="link" href="server-system-variables.html#sysvar_autocommit">
       <code class="option">
        --autocommit=0
       </code>
      </a>
      option. To set
          the variable using an option file, include these lines:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa13813607"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">autocommit</span><span class="token attr-value"><span class="token punctuation">=</span>0</span></code></pre>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_automatic_sp_privileges">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_automatic_sp_privileges">
       <code class="literal">
        automatic_sp_privileges
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045278007152">
     </a>
     <a class="indexterm" name="idm46045278006112">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for automatic_sp_privileges">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --automatic-sp-privileges[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_automatic_sp_privileges">
            automatic_sp_privileges
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      When this variable has a value of 1 (the default), the server
          automatically grants the
      <a class="link" href="privileges-provided.html#priv_execute">
       <code class="literal">
        EXECUTE
       </code>
      </a>
      and
      <a class="link" href="privileges-provided.html#priv_alter-routine">
       <code class="literal">
        ALTER ROUTINE
       </code>
      </a>
      privileges to the
          creator of a stored routine, if the user cannot already
          execute and alter or drop the routine. (The
      <a class="link" href="privileges-provided.html#priv_alter-routine">
       <code class="literal">
        ALTER ROUTINE
       </code>
      </a>
      privilege is
          required to drop the routine.) The server also automatically
          drops those privileges from the creator when the routine is
          dropped. If
      <a class="link" href="server-system-variables.html#sysvar_automatic_sp_privileges">
       <code class="literal">
        automatic_sp_privileges
       </code>
      </a>
      is 0,
          the server does not automatically add or drop these
          privileges.
     </p>
     <p>
      The creator of a routine is the account used to execute the
      <code class="literal">
       CREATE
      </code>
      statement for it. This might not be
          the same as the account named as the
      <code class="literal">
       DEFINER
      </code>
      in the routine definition.
     </p>
     <p>
      If you start
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      with
      <a class="link" href="server-options.html#option_mysqld_skip-new">
       <code class="option">
        --skip-new
       </code>
      </a>
      ,
      <a class="link" href="server-system-variables.html#sysvar_automatic_sp_privileges">
       <code class="literal">
        automatic_sp_privileges
       </code>
      </a>
      is
          set to
      <code class="literal">
       OFF
      </code>
      .
     </p>
     <p>
      See also
      <a class="xref" href="stored-routines-privileges.html" title="27.2.2 Stored Routines and MySQL Privileges">
       Section 27.2.2, “Stored Routines and MySQL Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_auto_generate_certs">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_auto_generate_certs">
       <code class="literal">
        auto_generate_certs
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277967920">
     </a>
     <a class="indexterm" name="idm46045277966880">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for auto_generate_certs">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --auto-generate-certs[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_auto_generate_certs">
            auto_generate_certs
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls whether the server autogenerates SSL
          key and certificate files in the data directory, if they do
          not already exist.
     </p>
     <p>
      At startup, the server automatically generates server-side and
          client-side SSL certificate and key files in the data
          directory if the
      <a class="link" href="server-system-variables.html#sysvar_auto_generate_certs">
       <code class="literal">
        auto_generate_certs
       </code>
      </a>
      system
          variable is enabled and the server-side SSL files are missing
          from the data directory. These certificates are always
          generated in such cases, regardless of the values of any other
          TLS options. The certificate and key files enable secure
          client connections using SSL; see
      <a class="xref" href="using-encrypted-connections.html" title="8.3.1 Configuring MySQL to Use Encrypted Connections">
       Section 8.3.1, “Configuring MySQL to Use Encrypted Connections”
      </a>
      .
     </p>
     <p>
      For more information about SSL file autogeneration, including
          file names and characteristics, see
      <a class="xref" href="creating-ssl-rsa-files-using-mysql.html" title="8.3.3.1 Creating SSL and RSA Certificates and Keys using MySQL">
       Section 8.3.3.1, “Creating SSL and RSA Certificates and Keys using MySQL”
      </a>
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_sha256_password_auto_generate_rsa_keys">
       <code class="literal">
        sha256_password_auto_generate_rsa_keys
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_caching_sha2_password_auto_generate_rsa_keys">
       <code class="literal">
        caching_sha2_password_auto_generate_rsa_keys
       </code>
      </a>
      system variables are related but control autogeneration of RSA
          key-pair files needed for secure password exchange using RSA
          over unencrypted connections.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_back_log">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_back_log">
       <code class="literal">
        back_log
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277934944">
     </a>
     <a class="indexterm" name="idm46045277933856">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for back_log">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --back-log=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_back_log">
            back_log
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           -1
          </code>
          (signifies autosizing; do not assign this literal value)
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           65535
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of outstanding connection requests MySQL can have.
          This comes into play when the main MySQL thread gets very many
          connection requests in a very short time. It then takes some
          time (although very little) for the main thread to check the
          connection and start a new thread. The
      <a class="link" href="server-system-variables.html#sysvar_back_log">
       <code class="literal">
        back_log
       </code>
      </a>
      value indicates how
          many requests can be stacked during this short time before
          MySQL momentarily stops answering new requests. You need to
          increase this only if you expect a large number of connections
          in a short period of time.
     </p>
     <p>
      In other words, this value is the size of the listen queue for
          incoming TCP/IP connections. Your operating system has its own
          limit on the size of this queue. The manual page for the Unix
      <code class="literal">
       listen()
      </code>
      system call should have more
          details. Check your OS documentation for the maximum value for
          this variable.
      <a class="link" href="server-system-variables.html#sysvar_back_log">
       <code class="literal">
        back_log
       </code>
      </a>
      cannot be set higher than your operating system limit.
     </p>
     <p>
      The default value is the value of
      <a class="link" href="server-system-variables.html#sysvar_max_connections">
       <code class="literal">
        max_connections
       </code>
      </a>
      , which
          enables the permitted backlog to adjust to the maximum
          permitted number of connections.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_basedir">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_basedir">
       <code class="literal">
        basedir
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277898032">
     </a>
     <a class="indexterm" name="idm46045277896960">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for basedir">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --basedir=dir_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_basedir">
            basedir
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Directory name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           parent of mysqld installation directory
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The path to the MySQL installation base directory.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_big_tables">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_big_tables">
       <code class="literal">
        big_tables
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277872480">
     </a>
     <a class="indexterm" name="idm46045277871392">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for big_tables">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --big-tables[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_big_tables">
            big_tables
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <a class="indexterm" name="idm46045277849808">
     </a>
     <p>
      If enabled, the server stores all temporary tables on disk
          rather than in memory. This prevents most
      <code class="literal">
       The table
       <em class="replaceable">
        <code>
         tbl_name
        </code>
       </em>
       is full
      </code>
      errors
          for
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      operations that
          require a large temporary table, but also slows down queries
          for which in-memory tables would suffice.
     </p>
     <p>
      The default value for new connections is
      <code class="literal">
       OFF
      </code>
      (use in-memory temporary tables).
          Normally, it should never be necessary to enable this
          variable. When in-memory
      <span class="emphasis">
       <em>
        internal
       </em>
      </span>
      temporary tables are managed by the
      <code class="literal">
       TempTable
      </code>
      storage engine (the default), and
          the maximum amount of memory that can be occupied by the
      <code class="literal">
       TempTable
      </code>
      storage engine is exceeded, the
      <code class="literal">
       TempTable
      </code>
      storage engine starts storing
          data to temporary files on disk. When in-memory temporary
          tables are managed by the
      <code class="literal">
       MEMORY
      </code>
      storage
          engine, in-memory tables are automatically converted to
          disk-based tables as required. For more information, see
      <a class="xref" href="internal-temporary-tables.html" title="10.4.4 Internal Temporary Table Use in MySQL">
       Section 10.4.4, “Internal Temporary Table Use in MySQL”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_bind_address">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_bind_address">
       <code class="literal">
        bind_address
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277837440">
     </a>
     <a class="indexterm" name="idm46045277836352">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for bind_address">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --bind-address=addr
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_bind_address">
            bind_address
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           *
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The MySQL server listens on one or more network sockets for
          TCP/IP connections. Each socket is bound to one address, but
          it is possible for an address to map onto multiple network
          interfaces. To specify how the server should listen for TCP/IP
          connections, set the
      <a class="link" href="server-system-variables.html#sysvar_bind_address">
       <code class="literal">
        bind_address
       </code>
      </a>
      system variable
          at server startup. The server also has an
      <a class="link" href="server-system-variables.html#sysvar_admin_address">
       <code class="literal">
        admin_address
       </code>
      </a>
      system variable
          that enables administrative connections on a dedicated
          interface. See
      <a class="xref" href="connection-interfaces.html" title="7.1.12.1 Connection Interfaces">
       Section 7.1.12.1, “Connection Interfaces”
      </a>
      .
     </p>
     <p>
      If
      <a class="link" href="server-system-variables.html#sysvar_bind_address">
       <code class="literal">
        bind_address
       </code>
      </a>
      is specified,
          it accepts a list of one or more address values, each of which
          may specify a single non-wildcard IP address or host name.
          Each address may include a network namespace specifier. If
          only one address is specified, it may make use of one of the
          wildcard address formats that permit listening on multiple
          network interfaces (
      <code class="literal">
       *
      </code>
      ,
      <code class="literal">
       0.0.0.0
      </code>
      , or
      <code class="literal">
       ::
      </code>
      ).
          Multiple addresses are separated by commas. When multiple
          values are listed, each value must specify a single
          non-wildcard IP address (either IPv4 or IPv6) or a host name,
          and wildcard address formats (
      <code class="literal">
       *
      </code>
      ,
      <code class="literal">
       0.0.0.0
      </code>
      , or
      <code class="literal">
       ::
      </code>
      ) are not
          allowed.
     </p>
     <p>
      IP addresses can be specified as IPv4 or IPv6 addresses. For
          any value that is a host name, the server resolves the name to
          an IP address and binds to that address. If a host name
          resolves to multiple IP addresses, the server uses the first
          IPv4 address if there are any, or the first IPv6 address
          otherwise.
     </p>
     <p>
      The server treats different types of addresses as follows:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         If the address is
         <code class="literal">
          *
         </code>
         , the server accepts
              TCP/IP connections on all server host IPv4 interfaces,
              and, if the server host supports IPv6, on all IPv6
              interfaces. Use this address to permit both IPv4 and IPv6
              connections on all server interfaces. This value is the
              default. If the variable specifies a list of multiple
              values, this value is not permitted.
        </p>
       </li>
       <li class="listitem">
        <p>
         If the address is
         <code class="literal">
          0.0.0.0
         </code>
         , the server
              accepts TCP/IP connections on all server host IPv4
              interfaces. If the variable specifies a list of multiple
              values, this value is not permitted.
        </p>
       </li>
       <li class="listitem">
        <p>
         If the address is
         <code class="literal">
          ::
         </code>
         , the server
              accepts TCP/IP connections on all server host IPv4 and
              IPv6 interfaces. If the variable specifies a list of
              multiple values, this value is not permitted.
        </p>
       </li>
       <li class="listitem">
        <p>
         If the address is an IPv4-mapped address, the server
              accepts TCP/IP connections for that address, in either
              IPv4 or IPv6 format. For example, if the server is bound
              to
         <code class="literal">
          ::ffff:127.0.0.1
         </code>
         , clients can
              connect using
         <code class="option">
          --host=127.0.0.1
         </code>
         or
         <code class="option">
          --host=::ffff:127.0.0.1
         </code>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         If the address is a
         <span class="quote">
          “
          <span class="quote">
           regular
          </span>
          ”
         </span>
         IPv4 or IPv6
              address (such as
         <code class="literal">
          127.0.0.1
         </code>
         or
         <code class="literal">
          ::1
         </code>
         ), the server accepts TCP/IP
              connections only for that IPv4 or IPv6 address.
        </p>
       </li>
      </ul>
     </div>
     <p>
      These rules apply to specifying a network namespace for an
          address:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         A network namespace can be specified for an IP address or
              a host name.
        </p>
       </li>
       <li class="listitem">
        <p>
         A network namespace cannot be specified for a wildcard IP
              address.
        </p>
       </li>
       <li class="listitem">
        <p>
         For a given address, the network namespace is optional. If
              given, it must be specified as a
         <code class="literal">
          /
          <em class="replaceable">
           <code>
            ns
           </code>
          </em>
         </code>
         suffix
              immediately following the address.
        </p>
       </li>
       <li class="listitem">
        <p>
         An address with no
         <code class="literal">
          /
          <em class="replaceable">
           <code>
            ns
           </code>
          </em>
         </code>
         suffix
              uses the host system global namespace. The global
              namespace is therefore the default.
        </p>
       </li>
       <li class="listitem">
        <p>
         An address with a
         <code class="literal">
          /
          <em class="replaceable">
           <code>
            ns
           </code>
          </em>
         </code>
         suffix
              uses the namespace named
         <em class="replaceable">
          <code>
           ns
          </code>
         </em>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         The host system must support network namespaces and each
              named namespace must previously have been set up. Naming a
              nonexistent namespace produces an error.
        </p>
       </li>
       <li class="listitem">
        <p>
         If the variable value specifies multiple addresses, it can
              include addresses in the global namespace, in named
              namespaces, or a mix.
        </p>
       </li>
      </ul>
     </div>
     <p>
      For additional information about network namespaces, see
      <a class="xref" href="network-namespace-support.html" title="7.1.14 Network Namespace Support">
       Section 7.1.14, “Network Namespace Support”
      </a>
      .
     </p>
     <p>
      If binding to any address fails, the server produces an error
          and does not start.
     </p>
     <p>
      Examples:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          bind_address=*
         </code>
        </p>
        <p>
         The server listens on all IPv4 or IPv6 addresses, as
              specified by the
         <code class="literal">
          *
         </code>
         wildcard.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          bind_address=198.51.100.20
         </code>
        </p>
        <p>
         The server listens only on the
         <code class="literal">
          198.51.100.20
         </code>
         IPv4 address.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          bind_address=198.51.100.20,2001:db8:0:f101::1
         </code>
        </p>
        <p>
         The server listens on the
         <code class="literal">
          198.51.100.20
         </code>
         IPv4 address and the
         <code class="literal">
          2001:db8:0:f101::1
         </code>
         IPv6 address.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          bind_address=198.51.100.20,*
         </code>
        </p>
        <p>
         This produces an error because wildcard addresses are not
              permitted when
         <a class="link" href="server-system-variables.html#sysvar_bind_address">
          <code class="literal">
           bind_address
          </code>
         </a>
         names a list
              of multiple values.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          bind_address=198.51.100.20/red,2001:db8:0:f101::1/blue,192.0.2.50
         </code>
        </p>
        <p>
         The server listens on the
         <code class="literal">
          198.51.100.20
         </code>
         IPv4 address in the
         <code class="literal">
          red
         </code>
         namespace, the
         <code class="literal">
          2001:db8:0:f101::1
         </code>
         IPv6 address in the
         <code class="literal">
          blue
         </code>
         namespace, and the
         <code class="literal">
          192.0.2.50
         </code>
         IPv4 address in the global
              namespace.
        </p>
       </li>
      </ul>
     </div>
     <p>
      When
      <a class="link" href="server-system-variables.html#sysvar_bind_address">
       <code class="literal">
        bind_address
       </code>
      </a>
      names a
          single value (wildcard or non-wildcard), the server listens on
          a single socket, which for a wildcard address may be bound to
          multiple network interfaces. When
      <a class="link" href="server-system-variables.html#sysvar_bind_address">
       <code class="literal">
        bind_address
       </code>
      </a>
      names a list of
          multiple values, the server listens on one socket per value,
          with each socket bound to a single network interface. The
          number of sockets is linear with the number of values
          specified. Depending on operating system connection-acceptance
          efficiency, long value lists might incur a performance penalty
          for accepting TCP/IP connections.
     </p>
     <p>
      <a class="indexterm" name="idm46045277757264">
      </a>
      Because file descriptors are allocated for listening sockets
          and network namespace files, it may be necessary to increase
          the
      <a class="link" href="server-system-variables.html#sysvar_open_files_limit">
       <code class="literal">
        open_files_limit
       </code>
      </a>
      system
          variable.
     </p>
     <p>
      If you intend to bind the server to a specific address, be
          sure that the
      <code class="literal">
       mysql.user
      </code>
      system table
          contains an account with administrative privileges that you
          can use to connect to that address. Otherwise, you cannot shut
          down the server. For example, if you bind the server to
      <code class="literal">
       *
      </code>
      , you can connect to it using all existing
          accounts. But if you bind the server to
      <code class="literal">
       ::1
      </code>
      , it accepts connections only on that
          address. In that case, first make sure that the
      <code class="literal">
       'root'@'::1'
      </code>
      account is present in the
      <code class="literal">
       mysql.user
      </code>
      table so you can still connect
          to the server to shut it down.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_block_encryption_mode">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_block_encryption_mode">
       <code class="literal">
        block_encryption_mode
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277747264">
     </a>
     <a class="indexterm" name="idm46045277746224">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for block_encryption_mode">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --block-encryption-mode=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_block_encryption_mode">
            block_encryption_mode
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           aes-128-ecb
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls the block encryption mode for
          block-based algorithms such as AES. It affects encryption for
      <a class="link" href="encryption-functions.html#function_aes-encrypt">
       <code class="literal">
        AES_ENCRYPT()
       </code>
      </a>
      and
      <a class="link" href="encryption-functions.html#function_aes-decrypt">
       <code class="literal">
        AES_DECRYPT()
       </code>
      </a>
      .
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_block_encryption_mode">
       <code class="literal">
        block_encryption_mode
       </code>
      </a>
      takes a
          value in
      <code class="literal">
       aes-
       <em class="replaceable">
        <code>
         keylen
        </code>
       </em>
       -
       <em class="replaceable">
        <code>
         mode
        </code>
       </em>
      </code>
      format, where
      <em class="replaceable">
       <code>
        keylen
       </code>
      </em>
      is the key
          length in bits and
      <em class="replaceable">
       <code>
        mode
       </code>
      </em>
      is the
          encryption mode. The value is not case-sensitive. Permitted
      <em class="replaceable">
       <code>
        keylen
       </code>
      </em>
      values are 128, 192, and
          256. Permitted
      <em class="replaceable">
       <code>
        mode
       </code>
      </em>
      values are
      <code class="literal">
       ECB
      </code>
      ,
      <code class="literal">
       CBC
      </code>
      ,
      <code class="literal">
       CFB1
      </code>
      ,
      <code class="literal">
       CFB8
      </code>
      ,
      <code class="literal">
       CFB128
      </code>
      , and
      <code class="literal">
       OFB
      </code>
      .
     </p>
     <p>
      For example, this statement causes the AES encryption
          functions to use a key length of 256 bits and the CBC mode:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa32838239"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> block_encryption_mode <span class="token operator">=</span> <span class="token string">'aes-256-cbc'</span><span class="token punctuation">;</span></code></pre>
     </div>
     <p>
      An error occurs for attempts to set
      <a class="link" href="server-system-variables.html#sysvar_block_encryption_mode">
       <code class="literal">
        block_encryption_mode
       </code>
      </a>
      to a
          value containing an unsupported key length or a mode that the
          SSL library does not support.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_build_id">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_build_id">
       <code class="literal">
        build_id
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277706112">
     </a>
     <a class="indexterm" name="idm46045277705024">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for build_id">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_build_id">
            build_id
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Platform Specific
         </th>
         <td>
          Linux
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This is a 160-bit
      <code class="literal">
       SHA1
      </code>
      signature which is
          generated by the linker when compiling the server on Linux
          systems with
      <a class="link" href="source-configuration-options.html#option_cmake_with_build_id">
       <code class="option">
        -DWITH_BUILD_ID=ON
       </code>
      </a>
      (enabled by default), and converted to a hexadecimal string.
          This read-only value serves as a unique build ID, and is
          written into the server log at startup.
     </p>
     <p>
      <code class="literal">
       build_id
      </code>
      is not supported on platforms
          other than Linux.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_bulk_insert_buffer_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_bulk_insert_buffer_size">
       <code class="literal">
        bulk_insert_buffer_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277682304">
     </a>
     <a class="indexterm" name="idm46045277681264">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for bulk_insert_buffer_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --bulk-insert-buffer-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_bulk_insert_buffer_size">
            bulk_insert_buffer_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           8388608
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes/thread
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      <code class="literal">
       MyISAM
      </code>
      uses a special tree-like cache to
          make bulk inserts faster for
      <a class="link" href="insert-select.html" title="15.2.7.1 INSERT ... SELECT Statement">
       <code class="literal">
        INSERT ...
          SELECT
       </code>
      </a>
      ,
      <code class="literal">
       INSERT ... VALUES (...), (...),
          ...
      </code>
      , and
      <a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
       <code class="literal">
        LOAD DATA
       </code>
      </a>
      when adding data to nonempty tables. This variable limits the
          size of the cache tree in bytes per thread. Setting it to 0
          disables this optimization. The default value is 8MB.
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_caching_sha2_password_digest_rounds">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_caching_sha2_password_digest_rounds">
       <code class="literal">
        caching_sha2_password_digest_rounds
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277641728">
     </a>
     <a class="indexterm" name="idm46045277640688">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for caching_sha2_password_digest_rounds">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --caching-sha2-password-digest-rounds=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_caching_sha2_password_digest_rounds">
            caching_sha2_password_digest_rounds
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           5000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           5000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4095000
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of hash rounds used by the
      <code class="literal">
       caching_sha2_password
      </code>
      authentication plugin
          for password storage.
     </p>
     <p>
      Increasing the number of hashing rounds above the default
          value incurs a performance penalty that correlates with the
          amount of increase:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         Creating an account that uses the
         <code class="literal">
          caching_sha2_password
         </code>
         plugin has no
              impact on the client session within which the account is
              created, but the server must perform the hashing rounds to
              complete the operation.
        </p>
       </li>
       <li class="listitem">
        <p>
         For client connections that use the account, the server
              must perform the hashing rounds and save the result in the
              cache. The result is longer login time for the first
              client connection, but not for subsequent connections.
              This behavior occurs after each server restart.
        </p>
       </li>
      </ul>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_caching_sha2_password_auto_generate_rsa_keys">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_caching_sha2_password_auto_generate_rsa_keys">
       <code class="literal">
        caching_sha2_password_auto_generate_rsa_keys
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277606400">
     </a>
     <a class="indexterm" name="idm46045277605280">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for caching_sha2_password_auto_generate_rsa_keys">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --caching-sha2-password-auto-generate-rsa-keys[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_caching_sha2_password_auto_generate_rsa_keys">
            caching_sha2_password_auto_generate_rsa_keys
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The server uses this variable to determine whether to
          autogenerate RSA private/public key-pair files in the data
          directory if they do not already exist.
     </p>
     <p>
      At startup, the server automatically generates RSA
          private/public key-pair files in the data directory if all of
          these conditions are true: The
      <a class="link" href="server-system-variables.html#sysvar_sha256_password_auto_generate_rsa_keys">
       <code class="literal">
        sha256_password_auto_generate_rsa_keys
       </code>
      </a>
      or
      <a class="link" href="server-system-variables.html#sysvar_caching_sha2_password_auto_generate_rsa_keys">
       <code class="literal">
        caching_sha2_password_auto_generate_rsa_keys
       </code>
      </a>
      system variable is enabled; no RSA options are specified; the
          RSA files are missing from the data directory. These key-pair
          files enable secure password exchange using RSA over
          unencrypted connections for accounts authenticated by the
      <code class="literal">
       sha256_password
      </code>
      (deprecated) or
      <code class="literal">
       caching_sha2_password
      </code>
      plugin; see
      <a class="xref" href="sha256-pluggable-authentication.html" title="8.4.1.3 SHA-256 Pluggable Authentication">
       Section 8.4.1.3, “SHA-256 Pluggable Authentication”
      </a>
      , and
      <a class="xref" href="caching-sha2-pluggable-authentication.html" title="8.4.1.2 Caching SHA-2 Pluggable Authentication">
       Section 8.4.1.2, “Caching SHA-2 Pluggable Authentication”
      </a>
      .
     </p>
     <p>
      For more information about RSA file autogeneration, including
          file names and characteristics, see
      <a class="xref" href="creating-ssl-rsa-files-using-mysql.html" title="8.3.3.1 Creating SSL and RSA Certificates and Keys using MySQL">
       Section 8.3.3.1, “Creating SSL and RSA Certificates and Keys using MySQL”
      </a>
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_auto_generate_certs">
       <code class="literal">
        auto_generate_certs
       </code>
      </a>
      system variable is related but controls autogeneration of SSL
          certificate and key files needed for secure connections using
          SSL.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_caching_sha2_password_private_key_path">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_caching_sha2_password_private_key_path">
       <code class="literal">
        caching_sha2_password_private_key_path
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277570864">
     </a>
     <a class="indexterm" name="idm46045277569824">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for caching_sha2_password_private_key_path">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --caching-sha2-password-private-key-path=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_caching_sha2_password_private_key_path">
            caching_sha2_password_private_key_path
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           private_key.pem
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable specifies the path name of the RSA private key
          file for the
      <code class="literal">
       caching_sha2_password
      </code>
      authentication plugin. If the file is named as a relative
          path, it is interpreted relative to the server data directory.
          The file must be in PEM format.
     </p>
     <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Important
      </div>
      <p>
       Because this file stores a private key, its access mode
            should be restricted so that only the MySQL server can read
            it.
      </p>
     </div>
     <p>
      For information about
      <code class="literal">
       caching_sha2_password
      </code>
      , see
      <a class="xref" href="caching-sha2-pluggable-authentication.html" title="8.4.1.2 Caching SHA-2 Pluggable Authentication">
       Section 8.4.1.2, “Caching SHA-2 Pluggable Authentication”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_caching_sha2_password_public_key_path">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_caching_sha2_password_public_key_path">
       <code class="literal">
        caching_sha2_password_public_key_path
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277541248">
     </a>
     <a class="indexterm" name="idm46045277540208">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for caching_sha2_password_public_key_path">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --caching-sha2-password-public-key-path=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_caching_sha2_password_public_key_path">
            caching_sha2_password_public_key_path
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           public_key.pem
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable specifies the path name of the RSA public key
          file for the
      <code class="literal">
       caching_sha2_password
      </code>
      authentication plugin. If the file is named as a relative
          path, it is interpreted relative to the server data directory.
          The file must be in PEM format.
     </p>
     <p>
      For information about
      <code class="literal">
       caching_sha2_password
      </code>
      , including
          information about how clients request the RSA public key, see
      <a class="xref" href="caching-sha2-pluggable-authentication.html" title="8.4.1.2 Caching SHA-2 Pluggable Authentication">
       Section 8.4.1.2, “Caching SHA-2 Pluggable Authentication”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_character_set_client">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_character_set_client">
       <code class="literal">
        character_set_client
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277512656">
     </a>
     <a class="indexterm" name="idm46045277511616">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for character_set_client">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_character_set_client">
            character_set_client
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           utf8mb4
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The character set for statements that arrive from the client.
          The session value of this variable is set using the character
          set requested by the client when the client connects to the
          server. (Many clients support a
      <code class="option">
       --default-character-set
      </code>
      option to enable this
          character set to be specified explicitly. See also
      <a class="xref" href="charset-connection.html" title="12.4 Connection Character Sets and Collations">
       Section 12.4, “Connection Character Sets and Collations”
      </a>
      .) The global value of the
          variable is used to set the session value in cases when the
          client-requested value is unknown or not available, or the
          server is configured to ignore client requests. This can
          happen when the client requests a character set not known to
          the server, such as when a Japanese-enabled client requests
      <code class="literal">
       sjis
      </code>
      when connecting to a server not
          configured with
      <code class="literal">
       sjis
      </code>
      support.
     </p>
     <p>
      Some character sets cannot be used as the client character
          set. Attempting to use them as the
      <a class="link" href="server-system-variables.html#sysvar_character_set_client">
       <code class="literal">
        character_set_client
       </code>
      </a>
      value
          produces an error. See
      <a class="xref" href="charset-connection.html#charset-connection-impermissible-client-charset" title="Impermissible Client Character Sets">
       Impermissible Client Character Sets
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_character_set_connection">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_character_set_connection">
       <code class="literal">
        character_set_connection
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277483712">
     </a>
     <a class="indexterm" name="idm46045277482608">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for character_set_connection">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_character_set_connection">
            character_set_connection
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           utf8mb4
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The character set used for literals specified without a
          character set introducer and for number-to-string conversion.
          For information about introducers, see
      <a class="xref" href="charset-introducer.html" title="12.3.8 Character Set Introducers">
       Section 12.3.8, “Character Set Introducers”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_character_set_database">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_character_set_database">
       <code class="literal">
        character_set_database
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277459536">
     </a>
     <a class="indexterm" name="idm46045277458496">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for character_set_database">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_character_set_database">
            character_set_database
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           utf8mb4
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Footnote
         </th>
         <td>
          This option is dynamic, but should be set only by server. You should not set this variable manually.
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The character set used by the default database. The server
          sets this variable whenever the default database changes. If
          there is no default database, the variable has the same value
          as
      <a class="link" href="server-system-variables.html#sysvar_character_set_server">
       <code class="literal">
        character_set_server
       </code>
      </a>
      .
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
     <p>
      The global
      <a class="link" href="server-system-variables.html#sysvar_character_set_database">
       <code class="literal">
        character_set_database
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_collation_database">
       <code class="literal">
        collation_database
       </code>
      </a>
      system
          variables are deprecated; expect them to be removed in a
          future version of MySQL.
     </p>
     <p>
      Assigning a value to the session
      <a class="link" href="server-system-variables.html#sysvar_character_set_database">
       <code class="literal">
        character_set_database
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_collation_database">
       <code class="literal">
        collation_database
       </code>
      </a>
      system
          variables is deprecated and assignments produce a warning.
          Expect the session variables to become read-only (and
          assignments to them to produce an error) in a future version
          of MySQL in which it remains possible to access the session
          variables to determine the database character set and
          collation for the default database.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_character_set_filesystem">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_character_set_filesystem">
       <code class="literal">
        character_set_filesystem
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277425136">
     </a>
     <a class="indexterm" name="idm46045277424032">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for character_set_filesystem">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --character-set-filesystem=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_character_set_filesystem">
            character_set_filesystem
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           binary
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The file system character set. This variable is used to
          interpret string literals that refer to file names, such as in
          the
      <a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
       <code class="literal">
        LOAD DATA
       </code>
      </a>
      and
      <a class="link" href="select-into.html" title="15.2.13.1 SELECT ... INTO Statement">
       <code class="literal">
        SELECT ... INTO
          OUTFILE
       </code>
      </a>
      statements and the
      <a class="link" href="string-functions.html#function_load-file">
       <code class="literal">
        LOAD_FILE()
       </code>
      </a>
      function. Such file
          names are converted from
      <a class="link" href="server-system-variables.html#sysvar_character_set_client">
       <code class="literal">
        character_set_client
       </code>
      </a>
      to
      <a class="link" href="server-system-variables.html#sysvar_character_set_filesystem">
       <code class="literal">
        character_set_filesystem
       </code>
      </a>
      before the file opening attempt occurs. The default value is
      <code class="literal">
       binary
      </code>
      , which means that no conversion
          occurs. For systems on which multibyte file names are
          permitted, a different value may be more appropriate. For
          example, if the system represents file names using UTF-8, set
      <a class="link" href="server-system-variables.html#sysvar_character_set_filesystem">
       <code class="literal">
        character_set_filesystem
       </code>
      </a>
      to
      <code class="literal">
       'utf8mb4'
      </code>
      .
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_character_set_results">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_character_set_results">
       <code class="literal">
        character_set_results
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277388496">
     </a>
     <a class="indexterm" name="idm46045277387456">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for character_set_results">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_character_set_results">
            character_set_results
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           utf8mb4
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The character set used for returning query results to the
          client. This includes result data such as column values,
          result metadata such as column names, and error messages.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_character_set_server">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_character_set_server">
       <code class="literal">
        character_set_server
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277365136">
     </a>
     <a class="indexterm" name="idm46045277364096">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for character_set_server">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --character-set-server=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_character_set_server">
            character_set_server
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           utf8mb4
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The servers default character set. See
      <a class="xref" href="charset-configuration.html" title="12.15 Character Set Configuration">
       Section 12.15, “Character Set Configuration”
      </a>
      . If you set this
          variable, you should also set
      <a class="link" href="server-system-variables.html#sysvar_collation_server">
       <code class="literal">
        collation_server
       </code>
      </a>
      to specify
          the collation for the character set.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_character_set_system">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_character_set_system">
       <code class="literal">
        character_set_system
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277337456">
     </a>
     <a class="indexterm" name="idm46045277336416">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for character_set_system">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_character_set_system">
            character_set_system
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           utf8mb3
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The character set used by the server for storing identifiers.
          The value is always
      <code class="literal">
       utf8mb3
      </code>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_character_sets_dir">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_character_sets_dir">
       <code class="literal">
        character_sets_dir
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277313552">
     </a>
     <a class="indexterm" name="idm46045277312512">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for character_sets_dir">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --character-sets-dir=dir_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_character_sets_dir">
            character_sets_dir
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Directory name
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The directory where character sets are installed. See
      <a class="xref" href="charset-configuration.html" title="12.15 Character Set Configuration">
       Section 12.15, “Character Set Configuration”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_check_proxy_users">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_check_proxy_users">
       <code class="literal">
        check_proxy_users
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277289696">
     </a>
     <a class="indexterm" name="idm46045277288656">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for check_proxy_users">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --check-proxy-users[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_check_proxy_users">
            check_proxy_users
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Some authentication plugins implement proxy user mapping for
          themselves (for example, the PAM and Windows authentication
          plugins). Other authentication plugins do not support proxy
          users by default. Of these, some can request that the MySQL
          server itself map proxy users according to granted proxy
          privileges:
      <code class="literal">
       mysql_native_password
      </code>
      (deprecated),
      <code class="literal">
       sha256_password
      </code>
      (deprecated).
     </p>
     <p>
      If the
      <a class="link" href="server-system-variables.html#sysvar_check_proxy_users">
       <code class="literal">
        check_proxy_users
       </code>
      </a>
      system variable is enabled, the server performs proxy user
          mapping for any authentication plugins that make such a
          request. It may also be necessary to enable plugin-specific
          system variables to take advantage of server proxy user
          mapping support:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         For the deprecated
         <code class="literal">
          mysql_native_password
         </code>
         plugin
              (deprecated), enable
         <a class="link" href="server-system-variables.html#sysvar_mysql_native_password_proxy_users">
          <code class="literal">
           mysql_native_password_proxy_users
          </code>
         </a>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         For the
         <code class="literal">
          sha256_password
         </code>
         plugin
              (deprecated), enable
         <a class="link" href="server-system-variables.html#sysvar_sha256_password_proxy_users">
          <code class="literal">
           sha256_password_proxy_users
          </code>
         </a>
         .
        </p>
       </li>
      </ul>
     </div>
     <p>
      For information about user proxying, see
      <a class="xref" href="proxy-users.html" title="8.2.19 Proxy Users">
       Section 8.2.19, “Proxy Users”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_collation_connection">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_collation_connection">
       <code class="literal">
        collation_connection
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277253104">
     </a>
     <a class="indexterm" name="idm46045277252064">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for collation_connection">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_collation_connection">
            collation_connection
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The collation of the connection character set.
      <a class="link" href="server-system-variables.html#sysvar_collation_connection">
       <code class="literal">
        collation_connection
       </code>
      </a>
      is
          important for comparisons of literal strings. For comparisons
          of strings with column values,
      <a class="link" href="server-system-variables.html#sysvar_collation_connection">
       <code class="literal">
        collation_connection
       </code>
      </a>
      does not
          matter because columns have their own collation, which has a
          higher collation precedence (see
      <a class="xref" href="charset-collation-coercibility.html" title="12.8.4 Collation Coercibility in Expressions">
       Section 12.8.4, “Collation Coercibility in Expressions”
      </a>
      ).
     </p>
     <p>
      Using the name of a user-defined collation for this variable
          raises a warning.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_collation_database">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_collation_database">
       <code class="literal">
        collation_database
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277228368">
     </a>
     <a class="indexterm" name="idm46045277227328">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for collation_database">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_collation_database">
            collation_database
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           utf8mb4_0900_ai_ci
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Footnote
         </th>
         <td>
          This option is dynamic, but should be set only by server. You should not set this variable manually.
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The collation used by the default database. The server sets
          this variable whenever the default database changes. If there
          is no default database, the variable has the same value as
      <a class="link" href="server-system-variables.html#sysvar_collation_server">
       <code class="literal">
        collation_server
       </code>
      </a>
      .
     </p>
     <p>
      The global
      <a class="link" href="server-system-variables.html#sysvar_character_set_database">
       <code class="literal">
        character_set_database
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_collation_database">
       <code class="literal">
        collation_database
       </code>
      </a>
      system
          variables are deprecated; expect them to be removed in a
          future version of MySQL.
     </p>
     <p>
      Assigning a value to the session
      <a class="link" href="server-system-variables.html#sysvar_character_set_database">
       <code class="literal">
        character_set_database
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_collation_database">
       <code class="literal">
        collation_database
       </code>
      </a>
      system
          variables is deprecated and assignments produce a warning.
          Expect the session variables to become read-only (and
          assignments to produce an error) in a future version of MySQL
          in which it remains possible to access the session variables
          to determine the database character set and collation for the
          default database.
     </p>
     <p>
      Using the name of a user-defined collation for
      <a class="link" href="server-system-variables.html#sysvar_collation_database">
       <code class="literal">
        collation_database
       </code>
      </a>
      raises a
          warning.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_collation_server">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_collation_server">
       <code class="literal">
        collation_server
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277193648">
     </a>
     <a class="indexterm" name="idm46045277192560">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for collation_server">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --collation-server=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_collation_server">
            collation_server
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           utf8mb4_0900_ai_ci
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The server's default collation. See
      <a class="xref" href="charset-configuration.html" title="12.15 Character Set Configuration">
       Section 12.15, “Character Set Configuration”
      </a>
      .
     </p>
     <p>
      Setting this to the name of a user-defined collation raises a
          warning.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_completion_type">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_completion_type">
       <code class="literal">
        completion_type
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277166912">
     </a>
     <a class="indexterm" name="idm46045277165824">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for completion_type">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --completion-type=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_completion_type">
            completion_type
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NO_CHAIN
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            NO_CHAIN
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            CHAIN
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            RELEASE
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            0
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            1
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            2
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The transaction completion type. This variable can take the
          values shown in the following table. The variable can be
          assigned using either the name values or corresponding integer
          values.
     </p>
     <div class="informaltable">
      <table summary="Permitted values for the completion_type system variable.">
       <colgroup>
        <col style="width: 10%"/>
        <col style="width: 75%"/>
       </colgroup>
       <thead>
        <tr>
         <th>
          Value
         </th>
         <th>
          Description
         </th>
        </tr>
       </thead>
       <tbody>
        <tr>
         <td>
          <code class="literal">
           NO_CHAIN
          </code>
          (or 0)
         </td>
         <td>
          <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
           <code class="literal">
            COMMIT
           </code>
          </a>
          and
          <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
           <code class="literal">
            ROLLBACK
           </code>
          </a>
          are unaffected. This is the default value.
         </td>
        </tr>
        <tr>
         <td>
          <code class="literal">
           CHAIN
          </code>
          (or 1)
         </td>
         <td>
          <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
           <code class="literal">
            COMMIT
           </code>
          </a>
          and
          <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
           <code class="literal">
            ROLLBACK
           </code>
          </a>
          are equivalent to
          <code class="literal">
           COMMIT AND CHAIN
          </code>
          and
          <code class="literal">
           ROLLBACK AND CHAIN
          </code>
          , respectively.
                (A new transaction starts immediately with the same
                isolation level as the just-terminated transaction.)
         </td>
        </tr>
        <tr>
         <td>
          <code class="literal">
           RELEASE
          </code>
          (or 2)
         </td>
         <td>
          <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
           <code class="literal">
            COMMIT
           </code>
          </a>
          and
          <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
           <code class="literal">
            ROLLBACK
           </code>
          </a>
          are equivalent to
          <code class="literal">
           COMMIT RELEASE
          </code>
          and
          <code class="literal">
           ROLLBACK RELEASE
          </code>
          , respectively. (The
                server disconnects after terminating the transaction.)
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_completion_type">
       <code class="literal">
        completion_type
       </code>
      </a>
      affects
          transactions that begin with
      <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
       <code class="literal">
        START
          TRANSACTION
       </code>
      </a>
      or
      <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
       <code class="literal">
        BEGIN
       </code>
      </a>
      and
          end with
      <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
       <code class="literal">
        COMMIT
       </code>
      </a>
      or
      <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
       <code class="literal">
        ROLLBACK
       </code>
      </a>
      . It
          does not apply to implicit commits resulting from execution of
          the statements listed in
      <a class="xref" href="implicit-commit.html" title="15.3.3 Statements That Cause an Implicit Commit">
       Section 15.3.3, “Statements That Cause an Implicit Commit”
      </a>
      . It
          also does not apply for
      <a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
       <code class="literal">
        XA
          COMMIT
       </code>
      </a>
      ,
      <a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
       <code class="literal">
        XA
          ROLLBACK
       </code>
      </a>
      , or when
      <a class="link" href="server-system-variables.html#sysvar_autocommit">
       <code class="literal">
        autocommit=1
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_component_scheduler.enabled">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_component_scheduler.enabled">
       <code class="literal">
        component_scheduler.enabled
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277098752">
     </a>
     <a class="indexterm" name="idm46045277097648">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for component_scheduler.enabled">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --component-scheduler.enabled[=value]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_component_scheduler.enabled">
            component_scheduler.enabled
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      When set to
      <code class="literal">
       OFF
      </code>
      at startup, the background
          thread does not start. Tasks can still be scheduled, but they
          do not run until
      <code class="literal">
       component_scheduler
      </code>
      is
          enabled. When set to
      <code class="literal">
       ON
      </code>
      at startup, the
          component is fully operational.
     </p>
     <p>
      It is also possible to set the value dynamically to get the
          following effects:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          ON
         </code>
         starts the background thread that
              begins servicing the queue immediately.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          OFF
         </code>
         signals a termination of the
              background thread, which waits for it to end. The
              background thread checks the termination flag before
              accessing the queue to check for tasks to execute.
        </p>
       </li>
      </ul>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_concurrent_insert">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_concurrent_insert">
       <code class="literal">
        concurrent_insert
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277066656">
     </a>
     <a class="indexterm" name="idm46045277065616">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for concurrent_insert">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --concurrent-insert[=value]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_concurrent_insert">
            concurrent_insert
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           AUTO
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            NEVER
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            AUTO
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            ALWAYS
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            0
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            1
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            2
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If
      <code class="literal">
       AUTO
      </code>
      (the default), MySQL permits
      <a class="link" href="insert.html" title="15.2.7 INSERT Statement">
       <code class="literal">
        INSERT
       </code>
      </a>
      and
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      statements to run
          concurrently for
      <code class="literal">
       MyISAM
      </code>
      tables that have no
          free blocks in the middle of the data file.
     </p>
     <p>
      This variable can take the values shown in the following
          table. The variable can be assigned using either the name
          values or corresponding integer values.
     </p>
     <div class="informaltable">
      <table summary="Permitted values for the concurrent_insert system variable.">
       <colgroup>
        <col style="width: 10%"/>
        <col style="width: 75%"/>
       </colgroup>
       <thead>
        <tr>
         <th>
          Value
         </th>
         <th>
          Description
         </th>
        </tr>
       </thead>
       <tbody>
        <tr>
         <td>
          <code class="literal">
           NEVER
          </code>
          (or 0)
         </td>
         <td>
          Disables concurrent inserts
         </td>
        </tr>
        <tr>
         <td>
          <code class="literal">
           AUTO
          </code>
          (or 1)
         </td>
         <td>
          (Default) Enables concurrent insert for
          <code class="literal">
           MyISAM
          </code>
          tables
                that do not have holes
         </td>
        </tr>
        <tr>
         <td>
          <code class="literal">
           ALWAYS
          </code>
          (or 2)
         </td>
         <td>
          Enables concurrent inserts for all
          <code class="literal">
           MyISAM
          </code>
          tables,
                even those that have holes. For a table with a hole, new
                rows are inserted at the end of the table if it is in
                use by another thread. Otherwise, MySQL acquires a
                normal write lock and inserts the row into the hole.
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If you start
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      with
      <a class="link" href="server-options.html#option_mysqld_skip-new">
       <code class="option">
        --skip-new
       </code>
      </a>
      ,
      <a class="link" href="server-system-variables.html#sysvar_concurrent_insert">
       <code class="literal">
        concurrent_insert
       </code>
      </a>
      is set to
      <code class="literal">
       NEVER
      </code>
      .
     </p>
     <p>
      See also
      <a class="xref" href="concurrent-inserts.html" title="10.11.3 Concurrent Inserts">
       Section 10.11.3, “Concurrent Inserts”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_connect_timeout">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_connect_timeout">
       <code class="literal">
        connect_timeout
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045277007888">
     </a>
     <a class="indexterm" name="idm46045277006816">
     </a>
     <a class="indexterm" name="idm46045277005728">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for connect_timeout">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --connect-timeout=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_connect_timeout">
            connect_timeout
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           10
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           2
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of seconds that the
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      server waits for a connect packet before responding with
      <code class="literal">
       Bad handshake
      </code>
      . The default value is 10
          seconds.
     </p>
     <p>
      Increasing the
      <a class="link" href="server-system-variables.html#sysvar_connect_timeout">
       <code class="literal">
        connect_timeout
       </code>
      </a>
      value might
          help if clients frequently encounter errors of the form
      <code class="literal">
       Lost connection to MySQL server at
          '
       <em class="replaceable">
        <code>
         XXX
        </code>
       </em>
       ', system error:
       <em class="replaceable">
        <code>
         errno
        </code>
       </em>
      </code>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_connection_memory_chunk_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_connection_memory_chunk_size">
       <code class="literal">
        connection_memory_chunk_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276968992">
     </a>
     <a class="indexterm" name="idm46045276967888">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for connection_memory_chunk_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --connection-memory-chunk-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_connection_memory_chunk_size">
            connection_memory_chunk_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           8192
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           536870912
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Set the chunking size for updates to the global memory usage
          counter
      <a class="link" href="server-status-variables.html#statvar_Global_connection_memory">
       <code class="literal">
        Global_connection_memory
       </code>
      </a>
      .
          The status variable is updated only when total memory
          consumption by all user connections changes by more than this
          amount. Disable updates by setting
      <code class="literal">
       connection_memory_chunk_size = 0
      </code>
      .
     </p>
     <p>
      The memory calculation is exclusive of any memory used by
          system users such as the MySQL root user. Memory used by the
      <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
       <code class="literal">
        InnoDB
       </code>
      </a>
      buffer pool is also not
          included.
     </p>
     <p>
      You must have the
      <a class="link" href="privileges-provided.html#priv_system-variables-admin">
       <code class="literal">
        SYSTEM_VARIABLES_ADMIN
       </code>
      </a>
      or
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege to set this
          variable.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_connection_memory_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_connection_memory_limit">
       <code class="literal">
        connection_memory_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276929360">
     </a>
     <a class="indexterm" name="idm46045276928320">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for connection_memory_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --connection-memory-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_connection_memory_limit">
            connection_memory_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           2097152
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Set the maximum amount of memory that can be used by a single
          user connection. If any user connection uses more than this
          amount, all queries from this connection are rejected with
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_conn_limit" target="_top">
       <code class="literal">
        ER_CONN_LIMIT
       </code>
      </a>
      , including any
          queries currently running.
     </p>
     <p>
      The limit set by this variable does not apply to system users,
          or to the MySQL root account. Memory used by the
      <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
       <code class="literal">
        InnoDB
       </code>
      </a>
      buffer pool is also not
          included.
     </p>
     <p>
      You must have the
      <a class="link" href="privileges-provided.html#priv_system-variables-admin">
       <code class="literal">
        SYSTEM_VARIABLES_ADMIN
       </code>
      </a>
      or
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege to set this
          variable.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_core_file">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_core_file">
       <code class="literal">
        core_file
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276890672">
     </a>
     <a class="indexterm" name="idm46045276889584">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for core_file">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_core_file">
            core_file
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether to write a core file if the server unexpectedly exits.
          This variable is set by the
      <a class="link" href="server-options.html#option_mysqld_core-file">
       <code class="option">
        --core-file
       </code>
      </a>
      option.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_create_admin_listener_thread">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_create_admin_listener_thread">
       <code class="literal">
        create_admin_listener_thread
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276866480">
     </a>
     <a class="indexterm" name="idm46045276865376">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for create_admin_listener_thread">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --create-admin-listener-thread[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_create_admin_listener_thread">
            create_admin_listener_thread
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether to use a dedicated listening thread for client
          connections on the administrative network interface (see
      <a class="xref" href="connection-interfaces.html" title="7.1.12.1 Connection Interfaces">
       Section 7.1.12.1, “Connection Interfaces”
      </a>
      ). The default is
      <code class="literal">
       OFF
      </code>
      ; that is, the manager thread for
          ordinary connections on the main interface also handles
          connections for the administrative interface.
     </p>
     <p>
      Depending on factors such as platform type and workload, you
          may find one setting for this variable yields better
          performance than the other setting.
     </p>
     <p>
      Setting
      <a class="link" href="server-system-variables.html#sysvar_create_admin_listener_thread">
       <code class="literal">
        create_admin_listener_thread
       </code>
      </a>
      has no effect if
      <a class="link" href="server-system-variables.html#sysvar_admin_address">
       <code class="literal">
        admin_address
       </code>
      </a>
      is not
          specified because in that case the server maintains no
          administrative network interface.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_cte_max_recursion_depth">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_cte_max_recursion_depth">
       <code class="literal">
        cte_max_recursion_depth
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276835440">
     </a>
     <a class="indexterm" name="idm46045276834400">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for cte_max_recursion_depth">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --cte-max-recursion-depth=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_cte_max_recursion_depth">
            cte_max_recursion_depth
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The common table expression (CTE) maximum recursion depth. The
          server terminates execution of any CTE that recurses more
          levels than the value of this variable. For more information,
          see
      <a class="xref" href="with.html#common-table-expressions-recursion-limits" title="Limiting Common Table Expression Recursion">
       Limiting Common Table Expression Recursion
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_datadir">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_datadir">
       <code class="literal">
        datadir
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276803968">
     </a>
     <a class="indexterm" name="idm46045276802896">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for datadir">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --datadir=dir_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_datadir">
            datadir
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Directory name
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The path to the MySQL server data directory. Relative paths
          are resolved with respect to the current directory. If you
          expect the server to be started automatically (that is, in
          contexts for which you cannot know the current directory in
          advance), it is best to specify the
      <a class="link" href="server-system-variables.html#sysvar_datadir">
       <code class="literal">
        datadir
       </code>
      </a>
      value as an absolute
          path.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_debug">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_debug">
       <code class="literal">
        debug
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276779408">
     </a>
     <a class="indexterm" name="idm46045276778336">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for debug">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --debug[=debug_options]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_debug">
            debug
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Unix)
         </th>
         <td>
          <code class="literal">
           d:t:i:o,/tmp/mysqld.trace
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Windows)
         </th>
         <td>
          <code class="literal">
           d:t:i:O,\mysqld.trace
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable indicates the current debugging settings. It is
          available only for servers built with debugging support. The
          initial value comes from the value of instances of the
      <a class="link" href="server-options.html#option_mysqld_debug">
       <code class="option">
        --debug
       </code>
      </a>
      option given at server
          startup. The global and session values may be set at runtime.
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
     <p>
      Assigning a value that begins with
      <code class="literal">
       +
      </code>
      or
      <code class="literal">
       -
      </code>
      cause the value to added to or subtracted
          from the current value:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa8920973"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql&gt;</span> <span class="token keyword">SET</span> debug <span class="token operator">=</span> <span class="token string">'T'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql&gt;</span> <span class="token keyword">SELECT</span> <span class="token variable">@@debug</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @@debug <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> T       <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>

<span class="token prompt">mysql&gt;</span> <span class="token keyword">SET</span> debug <span class="token operator">=</span> <span class="token string">'+P'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql&gt;</span> <span class="token keyword">SELECT</span> <span class="token variable">@@debug</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @@debug <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> P:T     <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>

<span class="token prompt">mysql&gt;</span> <span class="token keyword">SET</span> debug <span class="token operator">=</span> <span class="token string">'-P'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql&gt;</span> <span class="token keyword">SELECT</span> <span class="token variable">@@debug</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> @@debug <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> T       <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
     </div>
     <p>
      For more information, see
      <a class="xref" href="dbug-package.html" title="7.9.4 The DBUG Package">
       Section 7.9.4, “The DBUG Package”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_debug_sync">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_debug_sync">
       <code class="literal">
        debug_sync
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276740400">
     </a>
     <a class="indexterm" name="idm46045276739312">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for debug_sync">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_debug_sync">
            debug_sync
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable is the user interface to the Debug Sync
          facility. Use of Debug Sync requires that MySQL be configured
          with the
      <a class="link" href="source-configuration-options.html#option_cmake_with_debug">
       <code class="option">
        -DWITH_DEBUG=ON
       </code>
      </a>
      <span class="command">
       <strong>
        CMake
       </strong>
      </span>
      option (see
      <a class="xref" href="source-configuration-options.html" title="2.8.7 MySQL Source-Configuration Options">
       Section 2.8.7, “MySQL Source-Configuration Options”
      </a>
      ); otherwise,
          this system variable is not available.
     </p>
     <p>
      The global variable value is read only and indicates whether
          the facility is enabled. By default, Debug Sync is disabled
          and the value of
      <a class="link" href="server-system-variables.html#sysvar_debug_sync">
       <code class="literal">
        debug_sync
       </code>
      </a>
      is
      <code class="literal">
       OFF
      </code>
      . If the server is started with
      <a class="link" href="server-options.html#option_mysqld_debug-sync-timeout">
       <code class="option">
        --debug-sync-timeout=
        <em class="replaceable">
         <code>
          N
         </code>
        </em>
       </code>
      </a>
      ,
          where
      <em class="replaceable">
       <code>
        N
       </code>
      </em>
      is a timeout value greater
          than 0, Debug Sync is enabled and the value of
      <a class="link" href="server-system-variables.html#sysvar_debug_sync">
       <code class="literal">
        debug_sync
       </code>
      </a>
      is
      <code class="literal">
       ON -
          current signal
      </code>
      followed by the signal name. Also,
      <em class="replaceable">
       <code>
        N
       </code>
      </em>
      becomes the default timeout for
          individual synchronization points.
     </p>
     <p>
      The session value can be read by any user and has the same
          value as the global variable. The session value can be set to
          control synchronization points.
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
     <p>
      For a description of the Debug Sync facility and how to use
          synchronization points, see
      <a class="ulink" href="/doc/internals/en/test-synchronization.html" target="_top">
       MySQL
          Internals: Test Synchronization
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_default_collation_for_utf8mb4">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_default_collation_for_utf8mb4">
       <code class="literal">
        default_collation_for_utf8mb4
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276707248">
     </a>
     <a class="indexterm" name="idm46045276706144">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for default_collation_for_utf8mb4">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_default_collation_for_utf8mb4">
            default_collation_for_utf8mb4
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            utf8mb4_0900_ai_ci
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            utf8mb4_general_ci
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Important
      </div>
      <p>
       The
       <code class="literal">
        default_collation_for_utf8mb4
       </code>
       system
            variable is for internal use by MySQL Replication only.
      </p>
     </div>
     <p>
      This variable is set by the server to the default collation
          for the
      <code class="literal">
       utf8mb4
      </code>
      character set. The value of
          the variable is replicated from a source to a replica so that
          the replica can correctly process data originating from a
          source with a different default collation for
      <code class="literal">
       utf8mb4
      </code>
      . This variable is primarily
          intended to support replication from a MySQL 5.7 or older
          replication source server to a later MySQL replica server, or
          group replication with a MySQL 5.7 primary node and one or
          more MySQL 8.0 or later secondaries. The default collation for
      <code class="literal">
       utf8mb4
      </code>
      in MySQL 5.7 is
      <code class="literal">
       utf8mb4_general_ci
      </code>
      , but
      <code class="literal">
       utf8mb4_0900_ai_ci
      </code>
      in later release series.
          The variable is not present in releases earlier than MySQL
          8.0, so if the replica does not receive a value for the
          variable, it assumes the source is from an earlier release and
          sets the value to the previous default collation
      <code class="literal">
       utf8mb4_general_ci
      </code>
      .
     </p>
     <p>
      The default
      <code class="literal">
       utf8mb4
      </code>
      collation is used in
          the following statements:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <a class="link" href="show-collation.html" title="15.7.7.5 SHOW COLLATION Statement">
          <code class="literal">
           SHOW COLLATION
          </code>
         </a>
         and
         <a class="link" href="show-character-set.html" title="15.7.7.4 SHOW CHARACTER SET Statement">
          <code class="literal">
           SHOW CHARACTER SET
          </code>
         </a>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
          <code class="literal">
           CREATE TABLE
          </code>
         </a>
         and
         <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
          <code class="literal">
           ALTER TABLE
          </code>
         </a>
         having a
         <code class="literal">
          CHARACTER SET utf8mb4
         </code>
         clause without a
         <code class="literal">
          COLLATION
         </code>
         clause, either for the table
              character set or for a column character set.
        </p>
       </li>
       <li class="listitem">
        <p>
         <a class="link" href="create-database.html" title="15.1.12 CREATE DATABASE Statement">
          <code class="literal">
           CREATE DATABASE
          </code>
         </a>
         and
         <a class="link" href="alter-database.html" title="15.1.2 ALTER DATABASE Statement">
          <code class="literal">
           ALTER DATABASE
          </code>
         </a>
         having a
         <code class="literal">
          CHARACTER SET utf8mb4
         </code>
         clause without a
         <code class="literal">
          COLLATION
         </code>
         clause.
        </p>
       </li>
       <li class="listitem">
        <p>
         Any statement containing a string literal of the form
         <code class="literal">
          _utf8mb4'
          <em class="replaceable">
           <code>
            some
              text
           </code>
          </em>
          '
         </code>
         without a
         <code class="literal">
          COLLATE
         </code>
         clause.
        </p>
       </li>
      </ul>
     </div>
     <p>
      See also
      <a class="xref" href="charset-unicode.html" title="12.9 Unicode Support">
       Section 12.9, “Unicode Support”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_default_password_lifetime">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_default_password_lifetime">
       <code class="literal">
        default_password_lifetime
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276656640">
     </a>
     <a class="indexterm" name="idm46045276655536">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for default_password_lifetime">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --default-password-lifetime=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_default_password_lifetime">
            default_password_lifetime
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           65535
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          days
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable defines the global automatic password expiration
          policy. The default
      <a class="link" href="server-system-variables.html#sysvar_default_password_lifetime">
       <code class="literal">
        default_password_lifetime
       </code>
      </a>
      value is 0, which disables automatic password expiration. If
          the value of
      <a class="link" href="server-system-variables.html#sysvar_default_password_lifetime">
       <code class="literal">
        default_password_lifetime
       </code>
      </a>
      is
          a positive integer
      <em class="replaceable">
       <code>
        N
       </code>
      </em>
      , it indicates
          the permitted password lifetime; passwords must be changed
          every
      <em class="replaceable">
       <code>
        N
       </code>
      </em>
      days.
     </p>
     <p>
      The global password expiration policy can be overridden as
          desired for individual accounts using the password expiration
          option of the
      <a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
       <code class="literal">
        CREATE USER
       </code>
      </a>
      and
      <a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
       <code class="literal">
        ALTER USER
       </code>
      </a>
      statements. See
      <a class="xref" href="password-management.html" title="8.2.15 Password Management">
       Section 8.2.15, “Password Management”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_default_storage_engine">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_default_storage_engine">
       <code class="literal">
        default_storage_engine
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276616688">
     </a>
     <a class="indexterm" name="idm46045276615648">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for default_storage_engine">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --default-storage-engine=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_default_storage_engine">
            default_storage_engine
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           InnoDB
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The default storage engine for tables. See
      <a class="xref" href="storage-engines.html" title="Chapter 18 Alternative Storage Engines">
       Chapter 18,
       <i>
        Alternative Storage Engines
       </i>
      </a>
      . This variable sets the
          storage engine for permanent tables only. To set the storage
          engine for
      <code class="literal">
       TEMPORARY
      </code>
      tables, set the
      <a class="link" href="server-system-variables.html#sysvar_default_tmp_storage_engine">
       <code class="literal">
        default_tmp_storage_engine
       </code>
      </a>
      system variable.
     </p>
     <p>
      To see which storage engines are available and enabled, use
          the
      <a class="link" href="show-engines.html" title="15.7.7.17 SHOW ENGINES Statement">
       <code class="literal">
        SHOW ENGINES
       </code>
      </a>
      statement or
          query the
      <code class="literal">
       INFORMATION_SCHEMA
      </code>
      <a class="link" href="information-schema-engines-table.html" title="28.3.13 The INFORMATION_SCHEMA ENGINES Table">
       <code class="literal">
        ENGINES
       </code>
      </a>
      table.
     </p>
     <p>
      If you disable the default storage engine at server startup,
          you must set the default engine for both permanent and
      <code class="literal">
       TEMPORARY
      </code>
      tables to a different engine, or
          else the server does not start.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_default_table_encryption">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_default_table_encryption">
       <code class="literal">
        default_table_encryption
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276582944">
     </a>
     <a class="indexterm" name="idm46045276581856">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for default_table_encryption">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --default-table-encryption[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_default_table_encryption">
            default_table_encryption
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Defines the default encryption setting applied to schemas and
          general tablespaces when they are created without specifying
          an
      <code class="literal">
       ENCRYPTION
      </code>
      clause.
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_default_table_encryption">
       <code class="literal">
        default_table_encryption
       </code>
      </a>
      variable is only applicable to user-created schemas and
          general tablespaces. It does not govern encryption of the
      <code class="literal">
       mysql
      </code>
      system tablespace.
     </p>
     <p>
      Setting the runtime value of
      <a class="link" href="server-system-variables.html#sysvar_default_table_encryption">
       <code class="literal">
        default_table_encryption
       </code>
      </a>
      requires the
      <a class="link" href="privileges-provided.html#priv_system-variables-admin">
       <code class="literal">
        SYSTEM_VARIABLES_ADMIN
       </code>
      </a>
      and
      <a class="link" href="privileges-provided.html#priv_table-encryption-admin">
       <code class="literal">
        TABLE_ENCRYPTION_ADMIN
       </code>
      </a>
      privileges, or the deprecated
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_default_table_encryption">
       <code class="literal">
        default_table_encryption
       </code>
      </a>
      supports
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
          PERSIST
       </code>
      </a>
      and
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
          PERSIST_ONLY
       </code>
      </a>
      syntax. See
      <a class="xref" href="persisted-system-variables.html" title="7.1.9.3 Persisted System Variables">
       Section 7.1.9.3, “Persisted System Variables”
      </a>
      .
     </p>
     <p>
      For more information, see
      <a class="xref" href="innodb-data-encryption.html#innodb-schema-tablespace-encryption-default" title="Defining an Encryption Default for Schemas and General Tablespaces">
       Defining an Encryption Default for Schemas and General Tablespaces
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_default_tmp_storage_engine">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_default_tmp_storage_engine">
       <code class="literal">
        default_tmp_storage_engine
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276542016">
     </a>
     <a class="indexterm" name="idm46045276540912">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for default_tmp_storage_engine">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --default-tmp-storage-engine=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_default_tmp_storage_engine">
            default_tmp_storage_engine
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           InnoDB
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The default storage engine for
      <code class="literal">
       TEMPORARY
      </code>
      tables (created with
      <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
       <code class="literal">
        CREATE TEMPORARY
          TABLE
       </code>
      </a>
      ). To set the storage engine for permanent
          tables, set the
      <a class="link" href="server-system-variables.html#sysvar_default_storage_engine">
       <code class="literal">
        default_storage_engine
       </code>
      </a>
      system
          variable. Also see the discussion of that variable regarding
          possible values.
     </p>
     <p>
      If you disable the default storage engine at server startup,
          you must set the default engine for both permanent and
      <code class="literal">
       TEMPORARY
      </code>
      tables to a different engine, or
          else the server does not start.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_default_week_format">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_default_week_format">
       <code class="literal">
        default_week_format
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276511488">
     </a>
     <a class="indexterm" name="idm46045276510448">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for default_week_format">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --default-week-format=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_default_week_format">
            default_week_format
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           7
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The default mode value to use for the
      <a class="link" href="date-and-time-functions.html#function_week">
       <code class="literal">
        WEEK()
       </code>
      </a>
      function. See
      <a class="xref" href="date-and-time-functions.html" title="14.7 Date and Time Functions">
       Section 14.7, “Date and Time Functions”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_delay_key_write">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_delay_key_write">
       <code class="literal">
        delay_key_write
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276479104">
     </a>
     <a class="indexterm" name="idm46045276478016">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for delay_key_write">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --delay-key-write[={OFF|ON|ALL}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_delay_key_write">
            delay_key_write
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            OFF
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            ON
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            ALL
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable specifies how to use delayed key writes. It
          applies only to
      <code class="literal">
       MyISAM
      </code>
      tables. Delayed key
          writing causes key buffers not to be flushed between writes.
          See also
      <a class="xref" href="myisam-start.html" title="18.2.1 MyISAM Startup Options">
       Section 18.2.1, “MyISAM Startup Options”
      </a>
      .
     </p>
     <p>
      This variable can have one of the following values to affect
          handling of the
      <code class="literal">
       DELAY_KEY_WRITE
      </code>
      table
          option that can be used in
      <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
       <code class="literal">
        CREATE
          TABLE
       </code>
      </a>
      statements.
     </p>
     <div class="informaltable">
      <table summary="Permitted values for the delay_key_write system variable.">
       <colgroup>
        <col style="width: 10%"/>
        <col style="width: 75%"/>
       </colgroup>
       <thead>
        <tr>
         <th>
          Option
         </th>
         <th>
          Description
         </th>
        </tr>
       </thead>
       <tbody>
        <tr>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
         <td>
          <code class="literal">
           DELAY_KEY_WRITE
          </code>
          is ignored.
         </td>
        </tr>
        <tr>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
         <td>
          MySQL honors any
          <code class="literal">
           DELAY_KEY_WRITE
          </code>
          option specified in
          <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
           <code class="literal">
            CREATE TABLE
           </code>
          </a>
          statements.
                This is the default value.
         </td>
        </tr>
        <tr>
         <td>
          <code class="literal">
           ALL
          </code>
         </td>
         <td>
          All new opened tables are treated as if they were created with the
          <code class="literal">
           DELAY_KEY_WRITE
          </code>
          option enabled.
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       If you set this variable to
       <code class="literal">
        ALL
       </code>
       , you
            should not use
       <code class="literal">
        MyISAM
       </code>
       tables from within
            another program (such as another MySQL server or
       <a class="link" href="myisamchk.html" title="6.6.4 myisamchk — MyISAM Table-Maintenance Utility">
        <span class="command">
         <strong>
          myisamchk
         </strong>
        </span>
       </a>
       ) when the tables are in use.
            Doing so leads to index corruption.
      </p>
     </div>
     <p>
      If
      <code class="literal">
       DELAY_KEY_WRITE
      </code>
      is enabled for a table,
          the key buffer is not flushed for the table on every index
          update, but only when the table is closed. This speeds up
          writes on keys a lot, but if you use this feature, you should
          add automatic checking of all
      <code class="literal">
       MyISAM
      </code>
      tables
          by starting the server with the
      <a class="link" href="server-system-variables.html#sysvar_myisam_recover_options">
       <code class="literal">
        myisam_recover_options
       </code>
      </a>
      system
          variable set (for example,
      <a class="link" href="server-system-variables.html#sysvar_myisam_recover_options">
       <code class="literal">
        myisam_recover_options='BACKUP,FORCE'
       </code>
      </a>
      ).
          See
      <a class="xref" href="server-system-variables.html" title="7.1.8 Server System Variables">
       Section 7.1.8, “Server System Variables”
      </a>
      , and
      <a class="xref" href="myisam-start.html" title="18.2.1 MyISAM Startup Options">
       Section 18.2.1, “MyISAM Startup Options”
      </a>
      .
     </p>
     <p>
      If you start
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      with
      <a class="link" href="server-options.html#option_mysqld_skip-new">
       <code class="option">
        --skip-new
       </code>
      </a>
      ,
      <a class="link" href="server-system-variables.html#sysvar_delay_key_write">
       <code class="literal">
        delay_key_write
       </code>
      </a>
      is set to
      <code class="literal">
       OFF
      </code>
      .
     </p>
     <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Warning
      </div>
      <p>
       If you enable external locking with
       <a class="link" href="server-options.html#option_mysqld_external-locking">
        <code class="option">
         --external-locking
        </code>
       </a>
       , there is
            no protection against index corruption for tables that use
            delayed key writes.
      </p>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_delayed_insert_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_delayed_insert_limit">
       <code class="literal">
        delayed_insert_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276412336">
     </a>
     <a class="indexterm" name="idm46045276411296">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for delayed_insert_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --delayed-insert-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_delayed_insert_limit">
            delayed_insert_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           100
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This system variable is deprecated (because
      <code class="literal">
       DELAYED
      </code>
      inserts are not supported), and you
          should expect it to be removed in a future release.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_delayed_insert_timeout">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_delayed_insert_timeout">
       <code class="literal">
        delayed_insert_timeout
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276376512">
     </a>
     <a class="indexterm" name="idm46045276375472">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for delayed_insert_timeout">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --delayed-insert-timeout=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_delayed_insert_timeout">
            delayed_insert_timeout
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           300
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This system variable is deprecated (because
      <code class="literal">
       DELAYED
      </code>
      inserts are not supported), and you
          should expect it to be removed in a future release.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_delayed_queue_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_delayed_queue_size">
       <code class="literal">
        delayed_queue_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276341072">
     </a>
     <a class="indexterm" name="idm46045276340032">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for delayed_queue_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --delayed-queue-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_delayed_queue_size">
            delayed_queue_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This system variable is deprecated (because
      <code class="literal">
       DELAYED
      </code>
      inserts are not supported), and you
          should expect it to be removed in a future release.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_disabled_storage_engines">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_disabled_storage_engines">
       <code class="literal">
        disabled_storage_engines
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276305328">
     </a>
     <a class="indexterm" name="idm46045276304224">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for disabled_storage_engines">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --disabled-storage-engines=engine[,engine]...
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_disabled_storage_engines">
            disabled_storage_engines
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           empty string
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable indicates which storage engines cannot be used
          to create tables or tablespaces. For example, to prevent new
      <code class="literal">
       MyISAM
      </code>
      or
      <code class="literal">
       FEDERATED
      </code>
      tables from being created, start the server with these lines
          in the server option file:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa52040265"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">disabled_storage_engines</span><span class="token attr-value"><span class="token punctuation">=</span>"MyISAM,FEDERATED"</span></code></pre>
     </div>
     <p>
      By default,
      <a class="link" href="server-system-variables.html#sysvar_disabled_storage_engines">
       <code class="literal">
        disabled_storage_engines
       </code>
      </a>
      is
          empty (no engines disabled), but it can be set to a
          comma-separated list of one or more engines (not
          case-sensitive). Any engine named in the value cannot be used
          to create tables or tablespaces with
      <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
       <code class="literal">
        CREATE TABLE
       </code>
      </a>
      or
      <a class="link" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
       <code class="literal">
        CREATE TABLESPACE
       </code>
      </a>
      , and cannot
          be used with
      <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       <code class="literal">
        ALTER TABLE ...
          ENGINE
       </code>
      </a>
      or
      <a class="link" href="alter-tablespace.html" title="15.1.10 ALTER TABLESPACE Statement">
       <code class="literal">
        ALTER
          TABLESPACE ... ENGINE
       </code>
      </a>
      to change the storage engine
          of existing tables or tablespaces. Attempts to do so result in
          an
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_disabled_storage_engine" target="_top">
       <code class="literal">
        ER_DISABLED_STORAGE_ENGINE
       </code>
      </a>
      error.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_disabled_storage_engines">
       <code class="literal">
        disabled_storage_engines
       </code>
      </a>
      does
          not restrict other DDL statements for existing tables, such as
      <a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
       <code class="literal">
        CREATE INDEX
       </code>
      </a>
      ,
      <a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
       <code class="literal">
        TRUNCATE TABLE
       </code>
      </a>
      ,
      <a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
       <code class="literal">
        ANALYZE TABLE
       </code>
      </a>
      ,
      <a class="link" href="drop-table.html" title="15.1.32 DROP TABLE Statement">
       <code class="literal">
        DROP TABLE
       </code>
      </a>
      , or
      <a class="link" href="drop-tablespace.html" title="15.1.33 DROP TABLESPACE Statement">
       <code class="literal">
        DROP TABLESPACE
       </code>
      </a>
      . This permits a
          smooth transition so that existing tables or tablespaces that
          use a disabled engine can be migrated to a permitted engine by
          means such as
      <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       <code class="literal">
        ALTER TABLE ...
          ENGINE
        <em class="replaceable">
         <code>
          permitted_engine
         </code>
        </em>
       </code>
      </a>
      .
     </p>
     <p>
      It is permitted to set the
      <a class="link" href="server-system-variables.html#sysvar_default_storage_engine">
       <code class="literal">
        default_storage_engine
       </code>
      </a>
      or
      <a class="link" href="server-system-variables.html#sysvar_default_tmp_storage_engine">
       <code class="literal">
        default_tmp_storage_engine
       </code>
      </a>
      system variable to a storage engine that is disabled. This
          could cause applications to behave erratically or fail,
          although that might be a useful technique in a development
          environment for identifying applications that use disabled
          engines, so that they can be modified.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_disabled_storage_engines">
       <code class="literal">
        disabled_storage_engines
       </code>
      </a>
      is
          disabled and has no effect if the server is started with any
          of these options:
      <a class="link" href="server-options.html#option_mysqld_initialize">
       <code class="option">
        --initialize
       </code>
      </a>
      ,
      <a class="link" href="server-options.html#option_mysqld_initialize-insecure">
       <code class="option">
        --initialize-insecure
       </code>
      </a>
      ,
      <a class="link" href="server-options.html#option_mysqld_skip-grant-tables">
       <code class="option">
        --skip-grant-tables
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_disconnect_on_expired_password">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_disconnect_on_expired_password">
       <code class="literal">
        disconnect_on_expired_password
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276250976">
     </a>
     <a class="indexterm" name="idm46045276249872">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for disconnect_on_expired_password">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --disconnect-on-expired-password[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_disconnect_on_expired_password">
            disconnect_on_expired_password
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls how the server handles clients with
          expired passwords:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         If the client indicates that it can handle expired
              passwords, the value of
         <a class="link" href="server-system-variables.html#sysvar_disconnect_on_expired_password">
          <code class="literal">
           disconnect_on_expired_password
          </code>
         </a>
         is irrelevant. The server permits the client to connect
              but puts it in sandbox mode.
        </p>
       </li>
       <li class="listitem">
        <p>
         If the client does not indicate that it can handle expired
              passwords, the server handles the client according to the
              value of
         <a class="link" href="server-system-variables.html#sysvar_disconnect_on_expired_password">
          <code class="literal">
           disconnect_on_expired_password
          </code>
         </a>
         :
        </p>
        <div class="itemizedlist">
         <ul class="itemizedlist" style="list-style-type: square; ">
          <li class="listitem">
           <p>
            If
            <a class="link" href="server-system-variables.html#sysvar_disconnect_on_expired_password">
             <code class="literal">
              disconnect_on_expired_password
             </code>
            </a>
            :
                  is enabled, the server disconnects the client.
           </p>
          </li>
          <li class="listitem">
           <p>
            If
            <a class="link" href="server-system-variables.html#sysvar_disconnect_on_expired_password">
             <code class="literal">
              disconnect_on_expired_password
             </code>
            </a>
            :
                  is disabled, the server permits the client to connect
                  but puts it in sandbox mode.
           </p>
          </li>
         </ul>
        </div>
       </li>
      </ul>
     </div>
     <p>
      For more information about the interaction of client and
          server settings relating to expired-password handling, see
      <a class="xref" href="expired-password-handling.html" title="8.2.16 Server Handling of Expired Passwords">
       Section 8.2.16, “Server Handling of Expired Passwords”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_div_precision_increment">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_div_precision_increment">
       <code class="literal">
        div_precision_increment
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276214192">
     </a>
     <a class="indexterm" name="idm46045276213152">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for div_precision_increment">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --div-precision-increment=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_div_precision_increment">
            div_precision_increment
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           4
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           30
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable indicates the number of digits by which to
          increase the scale of the result of division operations
          performed with the
      <a class="link" href="arithmetic-functions.html#operator_divide">
       <code class="literal">
        /
       </code>
      </a>
      operator.
          The default value is 4. The minimum and maximum values are 0
          and 30, respectively. The following example illustrates the
          effect of increasing the default value.
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-ini"><div class="docs-select-all right" id="sa79574625"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini">mysql&gt; SELECT 1/7;
+--------+
| 1/7    |
+--------+
| 0.1429 |
+--------+
mysql&gt; SET div_precision_increment <span class="token attr-value"><span class="token punctuation">=</span> 12;</span>
mysql&gt; SELECT 1/7;
+----------------+
| 1/7            |
+----------------+
| 0.142857142857 |
+----------------+</code></pre>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_dragnet.log_error_filter_rules">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_dragnet.log_error_filter_rules">
       <code class="literal">
        dragnet.log_error_filter_rules
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276178784">
     </a>
     <a class="indexterm" name="idm46045276177680">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for dragnet.log_error_filter_rules">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --dragnet.log-error-filter-rules=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_dragnet.log_error_filter_rules">
            dragnet.log_error_filter_rules
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           IF prio&gt;=INFORMATION THEN drop. IF EXISTS source_line THEN unset source_line.
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The filter rules that control operation of the
      <code class="literal">
       log_filter_dragnet
      </code>
      error log filter
          component. If
      <code class="literal">
       log_filter_dragnet
      </code>
      is not
          installed,
      <a class="link" href="server-system-variables.html#sysvar_dragnet.log_error_filter_rules">
       <code class="literal">
        dragnet.log_error_filter_rules
       </code>
      </a>
      is unavailable. If
      <code class="literal">
       log_filter_dragnet
      </code>
      is
          installed but not enabled, changes to
      <a class="link" href="server-system-variables.html#sysvar_dragnet.log_error_filter_rules">
       <code class="literal">
        dragnet.log_error_filter_rules
       </code>
      </a>
      have no effect.
     </p>
     <p>
      The effect of the default value is similar to the filtering
          performed by the
      <code class="literal">
       log_sink_internal
      </code>
      filter
          with a setting of
      <a class="link" href="server-system-variables.html#sysvar_log_error_verbosity">
       <code class="literal">
        log_error_verbosity=2
       </code>
      </a>
      .
     </p>
     <p>
      <a class="link" href="server-status-variables.html#statvar_dragnet.Status">
       <code class="literal">
        dragnet.Status
       </code>
      </a>
      status
          variable can be consulted to determine the result of the most
          recent assignment to
      <a class="link" href="server-system-variables.html#sysvar_dragnet.log_error_filter_rules">
       <code class="literal">
        dragnet.log_error_filter_rules
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_enterprise_encryption.maximum_rsa_key_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_enterprise_encryption.maximum_rsa_key_size">
       <code class="literal">
        enterprise_encryption.maximum_rsa_key_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276142416">
     </a>
     <a class="indexterm" name="idm46045276141296">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for enterprise_encryption.maximum_rsa_key_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --enterprise-encryption.maximum-rsa-key-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_enterprise_encryption.maximum_rsa_key_size">
            enterprise_encryption.maximum_rsa_key_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           4096
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           2048
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           16384
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable limits the maximum size of RSA keys generated by
          MySQL Enterprise Encryption. The variable is available only if
          the MySQL Enterprise Encryption component
      <code class="literal">
       component_enterprise_encryption
      </code>
      is
          installed.
     </p>
     <p>
      The lowest setting is 2048 bits, which is the minimum RSA key
          length that is acceptable by current best practice. The
          default setting is 4096 bits. The highest setting is 16384
          bits. Generating longer keys can consume significant CPU
          resources, so you can use this setting to limit keys to a
          length that provides adequate security for your requirements
          while balancing this with resource usage. See
      <a class="xref" href="enterprise-encryption-configuring.html" title="8.6.2 Configuring MySQL Enterprise Encryption">
       Section 8.6.2, “Configuring MySQL Enterprise Encryption”
      </a>
      for more
          information.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_enterprise_encryption.rsa_support_legacy_padding">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_enterprise_encryption.rsa_support_legacy_padding">
       <code class="literal">
        enterprise_encryption.rsa_support_legacy_padding
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276108880">
     </a>
     <a class="indexterm" name="idm46045276107760">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for enterprise_encryption.rsa_support_legacy_padding">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --enterprise-encryption.rsa_support_legacy_padding[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_enterprise_encryption.rsa_support_legacy_padding">
            enterprise_encryption.rsa_support_legacy_padding
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls whether encrypted data and signatures
          that MySQL Enterprise Encryption produced using the old
      <code class="literal">
       openssl_udf
      </code>
      shared library functions can be
          decrypted or verified by the MySQL Enterprise Encryption
          component
          (
      <code class="literal">
       component_enterprise_encryption
      </code>
      ). The
          variable is available only if the MySQL Enterprise Encryption
          component is installed.
     </p>
     <p>
      For the component functions to support decryption and
          verification for content produced by the old
      <code class="literal">
       openssl_udf
      </code>
      shared library functions, you
          must set the system variable padding to
      <code class="literal">
       ON
      </code>
      .
          When
      <code class="literal">
       ON
      </code>
      is set, if the component functions
          cannot decrypt or verify content when assuming it has the
          RSAES-OAEP or RSASSA-PSS scheme (as used by the component),
          they make another attempt assuming it has the RSAES-PKCS1-v1_5
          or RSASSA-PKCS1-v1_5 scheme (as used by the
      <code class="literal">
       openssl_udf
      </code>
      shared library functions). When
      <code class="literal">
       OFF
      </code>
      is set, if the component functions
          cannot decrypt or verify content using their normal schemes,
          they return null output. See
      <a class="xref" href="enterprise-encryption-configuring.html" title="8.6.2 Configuring MySQL Enterprise Encryption">
       Section 8.6.2, “Configuring MySQL Enterprise Encryption”
      </a>
      for more
          information.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_end_markers_in_json">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_end_markers_in_json">
       <code class="literal">
        end_markers_in_json
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276076000">
     </a>
     <a class="indexterm" name="idm46045276074960">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for end_markers_in_json">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --end-markers-in-json[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_end_markers_in_json">
            end_markers_in_json
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether optimizer JSON output should add end markers. See
      <a class="ulink" href="/doc/internals/en/end-markers-in-json-system-variable.html" target="_top">
       MySQL
          Internals: The end_markers_in_json System Variable
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_eq_range_index_dive_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_eq_range_index_dive_limit">
       <code class="literal">
        eq_range_index_dive_limit
       </code>
      </a>
     </p>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for eq_range_index_dive_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --eq-range-index-dive-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_eq_range_index_dive_limit">
            eq_range_index_dive_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           200
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable indicates the number of equality ranges in an
          equality comparison condition when the optimizer should switch
          from using index dives to index statistics in estimating the
          number of qualifying rows. It applies to evaluation of
          expressions that have either of these equivalent forms, where
          the optimizer uses a nonunique index to look up
      <em class="replaceable">
       <code>
        col_name
       </code>
      </em>
      values:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa36824180"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><em class="replaceable">col_name</em> <span class="token keyword">IN</span><span class="token punctuation">(</span><em class="replaceable">val1</em><span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">,</span> <em class="replaceable">valN</em><span class="token punctuation">)</span>
<em class="replaceable">col_name</em> <span class="token operator">=</span> <em class="replaceable">val1</em> <span class="token operator">OR</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token operator">OR</span> <em class="replaceable">col_name</em> <span class="token operator">=</span> <em class="replaceable">valN</em></code></pre>
     </div>
     <p>
      In both cases, the expression contains
      <em class="replaceable">
       <code>
        N
       </code>
      </em>
      equality ranges. The optimizer
          can make row estimates using index dives or index statistics.
          If
      <a class="link" href="server-system-variables.html#sysvar_eq_range_index_dive_limit">
       <code class="literal">
        eq_range_index_dive_limit
       </code>
      </a>
      is greater than 0, the optimizer uses existing index
          statistics instead of index dives if there are
      <a class="link" href="server-system-variables.html#sysvar_eq_range_index_dive_limit">
       <code class="literal">
        eq_range_index_dive_limit
       </code>
      </a>
      or
          more equality ranges. Thus, to permit use of index dives for
          up to
      <em class="replaceable">
       <code>
        N
       </code>
      </em>
      equality ranges, set
      <a class="link" href="server-system-variables.html#sysvar_eq_range_index_dive_limit">
       <code class="literal">
        eq_range_index_dive_limit
       </code>
      </a>
      to
      <em class="replaceable">
       <code>
        N
       </code>
      </em>
      + 1. To disable use of index
          statistics and always use index dives regardless of
      <em class="replaceable">
       <code>
        N
       </code>
      </em>
      , set
      <a class="link" href="server-system-variables.html#sysvar_eq_range_index_dive_limit">
       <code class="literal">
        eq_range_index_dive_limit
       </code>
      </a>
      to
          0.
     </p>
     <p>
      For more information, see
      <a class="xref" href="range-optimization.html#equality-range-optimization" title="Equality Range Optimization of Many-Valued Comparisons">
       Equality Range Optimization of Many-Valued Comparisons
      </a>
      .
     </p>
     <p>
      To update table index statistics for best estimates, use
      <a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
       <code class="literal">
        ANALYZE TABLE
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_error_count">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_error_count">
       <code class="literal">
        error_count
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276006368">
     </a>
     <a class="indexterm" name="idm46045276005280">
     </a>
     <p>
      The number of errors that resulted from the last statement
          that generated messages. This variable is read only. See
      <a class="xref" href="show-errors.html" title="15.7.7.18 SHOW ERRORS Statement">
       Section 15.7.7.18, “SHOW ERRORS Statement”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_event_scheduler">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_event_scheduler">
       <code class="literal">
        event_scheduler
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045276000064">
     </a>
     <a class="indexterm" name="idm46045275998976">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for event_scheduler">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --event-scheduler[=value]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_event_scheduler">
            event_scheduler
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            ON
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            OFF
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            DISABLED
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable enables or disables, and starts or stops, the
          Event Scheduler. The possible status values are
      <code class="literal">
       ON
      </code>
      ,
      <code class="literal">
       OFF
      </code>
      , and
      <code class="literal">
       DISABLED
      </code>
      . Turning the Event Scheduler
      <code class="literal">
       OFF
      </code>
      is not the same as disabling the Event
          Scheduler, which requires setting the status to
      <code class="literal">
       DISABLED
      </code>
      . This variable and its effects on
          the Event Scheduler's operation are discussed in greater
          detail in
      <a class="xref" href="events-configuration.html" title="27.4.2 Event Scheduler Configuration">
       Section 27.4.2, “Event Scheduler Configuration”
      </a>
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_explain_format">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_explain_format">
       <code class="literal">
        explain_format
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275965328">
     </a>
     <a class="indexterm" name="idm46045275964240">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for explain_format">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --explain-format=format
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_explain_format">
            explain_format
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           TRADITIONAL
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            TRADITIONAL (DEFAULT)
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            JSON
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            TREE
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable determines the default output format used by
      <a class="link" href="explain.html#explain-execution-plan" title="Obtaining Execution Plan Information">
       <code class="literal">
        EXPLAIN
       </code>
      </a>
      in the absence of a
      <code class="literal">
       FORMAT
      </code>
      option when
          displaying a query execution plan. Possible values and their
          effects are listed here:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          TRADITIONAL
         </code>
         : Use MySQL's
              traditional table-based output, as if
         <code class="literal">
          FORMAT=TRADITIONAL
         </code>
         had been specified
              as part of the
         <code class="literal">
          EXPLAIN
         </code>
         statement. This
              is the variable's default value.
         <code class="literal">
          DEFAULT
         </code>
         is also supported as a synonym
              for
         <code class="literal">
          TRADITIONAL
         </code>
         , and has exactly the
              same effect.
        </p>
        <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
         <div class="admon-title">
          Note
         </div>
         <p>
          <code class="literal">
           DEFAULT
          </code>
          cannot be used as part of an
          <code class="literal">
           EXPLAIN
          </code>
          statement's
          <code class="literal">
           FORMAT
          </code>
          option.
         </p>
        </div>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          JSON
         </code>
         : Use the JSON output format, as if
         <code class="literal">
          FORMAT=JSON
         </code>
         had been specified.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          TREE
         </code>
         : Use the tree-based output format,
              as if
         <code class="literal">
          FORMAT=TREE
         </code>
         had been specified.
        </p>
       </li>
      </ul>
     </div>
     <p>
      The setting for this variable also affects
      <code class="literal">
       EXPLAIN
          ANALYZE
      </code>
      . For this purpose,
      <code class="literal">
       DEFAULT
      </code>
      and
      <code class="literal">
       TRADITIONAL
      </code>
      are interpeted as
      <code class="literal">
       TREE
      </code>
      . If the value of
      <code class="literal">
       explain_format
      </code>
      is
      <code class="literal">
       JSON
      </code>
      and an
      <code class="literal">
       EXPLAIN ANALYZE
      </code>
      statement having no
      <code class="literal">
       FORMAT
      </code>
      option is issued, the statement
          raises an error
          (
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_not_supported_yet" target="_top">
       <code class="literal">
        ER_NOT_SUPPORTED_YET
       </code>
      </a>
      ).
     </p>
     <p>
      Using a format specifier with
      <code class="literal">
       EXPLAIN
      </code>
      or
      <code class="literal">
       EXPLAIN ANALYZE
      </code>
      overrides any setting for
      <code class="literal">
       explain_format
      </code>
      .
     </p>
     <p>
      The
      <code class="literal">
       explain_format
      </code>
      system variable has no
          effect on
      <code class="literal">
       EXPLAIN
      </code>
      output when this
          statement is used to display information about table columns.
     </p>
     <p>
      Setting the session value of
      <code class="literal">
       explain_format
      </code>
      requires no special privileges; setting it on the global level
          requires
      <a class="link" href="privileges-provided.html#priv_system-variables-admin">
       <code class="literal">
        SYSTEM_VARIABLES_ADMIN
       </code>
      </a>
      (or the deprecated
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege). See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
     <p>
      For more information and examples, see
      <a class="xref" href="explain.html#explain-execution-plan" title="Obtaining Execution Plan Information">
       Obtaining Execution Plan Information
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_explain_json_format_version">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_explain_json_format_version">
       <code class="literal">
        explain_json_format_version
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275902576">
     </a>
     <a class="indexterm" name="idm46045275901472">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for explain_json_format_version">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --explain-json-format-version=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_explain_json_format_version">
            explain_json_format_version
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Determines the version of the JSON output format used by
      <code class="literal">
       EXPLAIN FORMAT=JSON
      </code>
      statements. Setting
          this variable to
      <code class="literal">
       1
      </code>
      causes the server to use
          Version 1, which is the linear format used for output from
          such statements in older versions of MySQL; this is the
          default in MySQL 8.4. Setting
      <code class="literal">
       explain_json_format_version
      </code>
      to
      <code class="literal">
       2
      </code>
      causes the Version 2 format to be used;
          this JSON output format is based on access paths, and is
          intended to provide better compatibility with future versions
          of the MySQL Optimizer.
     </p>
     <p>
      For an example of use, see
      <a class="xref" href="explain.html#explain-execution-plan" title="Obtaining Execution Plan Information">
       Obtaining Execution Plan Information
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_explicit_defaults_for_timestamp">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_explicit_defaults_for_timestamp">
       <code class="literal">
        explicit_defaults_for_timestamp
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275867680">
     </a>
     <a class="indexterm" name="idm46045275866576">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for explicit_defaults_for_timestamp">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --explicit-defaults-for-timestamp[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_explicit_defaults_for_timestamp">
            explicit_defaults_for_timestamp
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This system variable determines whether the server enables
          certain nonstandard behaviors for default values and
      <code class="literal">
       NULL
      </code>
      -value handling in
      <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
       <code class="literal">
        TIMESTAMP
       </code>
      </a>
      columns. By default,
      <a class="link" href="server-system-variables.html#sysvar_explicit_defaults_for_timestamp">
       <code class="literal">
        explicit_defaults_for_timestamp
       </code>
      </a>
      is enabled, which disables the nonstandard behaviors.
          Disabling
      <a class="link" href="server-system-variables.html#sysvar_explicit_defaults_for_timestamp">
       <code class="literal">
        explicit_defaults_for_timestamp
       </code>
      </a>
      results in a warning.
     </p>
     <p>
      If
      <a class="link" href="server-system-variables.html#sysvar_explicit_defaults_for_timestamp">
       <code class="literal">
        explicit_defaults_for_timestamp
       </code>
      </a>
      is disabled, the server enables the nonstandard behaviors and
          handles
      <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
       <code class="literal">
        TIMESTAMP
       </code>
      </a>
      columns as
          follows:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
          <code class="literal">
           TIMESTAMP
          </code>
         </a>
         columns not
              explicitly declared with the
         <code class="literal">
          NULL
         </code>
         attribute are automatically declared with the
         <code class="literal">
          NOT
              NULL
         </code>
         attribute. Assigning such a column a value
              of
         <code class="literal">
          NULL
         </code>
         is permitted and sets the
              column to the current timestamp.
         <span class="emphasis">
          <em>
           Exception
          </em>
         </span>
         : Attempting to insert
         <code class="literal">
          NULL
         </code>
         into a generated column declared
              as
         <code class="literal">
          TIMESTAMP NOT NULL
         </code>
         is rejected with
              an error.
        </p>
       </li>
       <li class="listitem">
        <p>
         The first
         <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
          <code class="literal">
           TIMESTAMP
          </code>
         </a>
         column
              in a table, if not explicitly declared with the
         <code class="literal">
          NULL
         </code>
         attribute or an explicit
         <code class="literal">
          DEFAULT
         </code>
         or
         <code class="literal">
          ON UPDATE
         </code>
         attribute, is automatically declared with the
         <code class="literal">
          DEFAULT CURRENT_TIMESTAMP
         </code>
         and
         <code class="literal">
          ON UPDATE CURRENT_TIMESTAMP
         </code>
         attributes.
        </p>
       </li>
       <li class="listitem">
        <p>
         <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
          <code class="literal">
           TIMESTAMP
          </code>
         </a>
         columns following
              the first one, if not explicitly declared with the
         <code class="literal">
          NULL
         </code>
         attribute or an explicit
         <code class="literal">
          DEFAULT
         </code>
         attribute, are automatically
              declared as
         <code class="literal">
          DEFAULT '0000-00-00
              00:00:00'
         </code>
         (the
         <span class="quote">
          “
          <span class="quote">
           zero
          </span>
          ”
         </span>
         timestamp).
              For inserted rows that specify no explicit value for such
              a column, the column is assigned
         <code class="literal">
          '0000-00-00
              00:00:00'
         </code>
         and no warning occurs.
        </p>
        <p>
         Depending on whether strict SQL mode or the
         <a class="link" href="sql-mode.html#sqlmode_no_zero_date">
          <code class="literal">
           NO_ZERO_DATE
          </code>
         </a>
         SQL mode is
              enabled, a default value of
         <code class="literal">
          '0000-00-00
              00:00:00'
         </code>
         may be invalid. Be aware that the
         <a class="link" href="sql-mode.html#sqlmode_traditional">
          <code class="literal">
           TRADITIONAL
          </code>
         </a>
         SQL mode
              includes strict mode and
         <a class="link" href="sql-mode.html#sqlmode_no_zero_date">
          <code class="literal">
           NO_ZERO_DATE
          </code>
         </a>
         . See
         <a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
          Section 7.1.11, “Server SQL Modes”
         </a>
         .
        </p>
       </li>
      </ul>
     </div>
     <p>
      The nonstandard behaviors just described are deprecated;
          expect them to be removed in a future MySQL release.
     </p>
     <p>
      If
      <a class="link" href="server-system-variables.html#sysvar_explicit_defaults_for_timestamp">
       <code class="literal">
        explicit_defaults_for_timestamp
       </code>
      </a>
      is enabled, the server disables the nonstandard behaviors and
          handles
      <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
       <code class="literal">
        TIMESTAMP
       </code>
      </a>
      columns as
          follows:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         It is not possible to assign a
         <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
          <code class="literal">
           TIMESTAMP
          </code>
         </a>
         column a value of
         <code class="literal">
          NULL
         </code>
         to set it to the current
              timestamp. To assign the current timestamp, set the column
              to
         <a class="link" href="date-and-time-functions.html#function_current-timestamp">
          <code class="literal">
           CURRENT_TIMESTAMP
          </code>
         </a>
         or a
              synonym such as
         <a class="link" href="date-and-time-functions.html#function_now">
          <code class="literal">
           NOW()
          </code>
         </a>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
          <code class="literal">
           TIMESTAMP
          </code>
         </a>
         columns not
              explicitly declared with the
         <code class="literal">
          NOT NULL
         </code>
         attribute are automatically declared with the
         <code class="literal">
          NULL
         </code>
         attribute and permit
         <code class="literal">
          NULL
         </code>
         values. Assigning such a column a
              value of
         <code class="literal">
          NULL
         </code>
         sets it to
         <code class="literal">
          NULL
         </code>
         , not the current timestamp.
        </p>
       </li>
       <li class="listitem">
        <p>
         <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
          <code class="literal">
           TIMESTAMP
          </code>
         </a>
         columns declared
              with the
         <code class="literal">
          NOT NULL
         </code>
         attribute do not
              permit
         <code class="literal">
          NULL
         </code>
         values. For inserts that
              specify
         <code class="literal">
          NULL
         </code>
         for such a column, the
              result is either an error for a single-row insert if
              strict SQL mode is enabled, or
         <code class="literal">
          '0000-00-00
              00:00:00'
         </code>
         is inserted for multiple-row inserts
              with strict SQL mode disabled. In no case does assigning
              the column a value of
         <code class="literal">
          NULL
         </code>
         set it to
              the current timestamp.
        </p>
       </li>
       <li class="listitem">
        <p>
         <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
          <code class="literal">
           TIMESTAMP
          </code>
         </a>
         columns
              explicitly declared with the
         <code class="literal">
          NOT NULL
         </code>
         attribute and without an explicit
         <code class="literal">
          DEFAULT
         </code>
         attribute are treated as having
              no default value. For inserted rows that specify no
              explicit value for such a column, the result depends on
              the SQL mode. If strict SQL mode is enabled, an error
              occurs. If strict SQL mode is not enabled, the column is
              declared with the implicit default of
         <code class="literal">
          '0000-00-00
              00:00:00'
         </code>
         and a warning occurs. This is similar
              to how MySQL treats other temporal types such as
         <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
          <code class="literal">
           DATETIME
          </code>
         </a>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         No
         <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
          <code class="literal">
           TIMESTAMP
          </code>
         </a>
         column is
              automatically declared with the
         <code class="literal">
          DEFAULT
              CURRENT_TIMESTAMP
         </code>
         or
         <code class="literal">
          ON UPDATE
              CURRENT_TIMESTAMP
         </code>
         attributes. Those attributes
              must be explicitly specified.
        </p>
       </li>
       <li class="listitem">
        <p>
         The first
         <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
          <code class="literal">
           TIMESTAMP
          </code>
         </a>
         column
              in a table is not handled differently from
         <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
          <code class="literal">
           TIMESTAMP
          </code>
         </a>
         columns following
              the first one.
        </p>
       </li>
      </ul>
     </div>
     <p>
      If
      <a class="link" href="server-system-variables.html#sysvar_explicit_defaults_for_timestamp">
       <code class="literal">
        explicit_defaults_for_timestamp
       </code>
      </a>
      is disabled at server startup, this warning appears in the
          error log:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-simple"><div class="docs-select-all right" id="sa91915399"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple"><span class="token punctuation">[</span>Warning<span class="token punctuation">]</span> TIMESTAMP with implicit DEFAULT value is deprecated<span class="token punctuation">.</span>
Please use <span class="token operator">--</span>explicit_defaults_for_timestamp server option <span class="token punctuation">(</span>see
documentation for more details<span class="token punctuation">)</span><span class="token punctuation">.</span></code></pre>
     </div>
     <p>
      As indicated by the warning, to disable the deprecated
          nonstandard behaviors, enable the
      <a class="link" href="server-system-variables.html#sysvar_explicit_defaults_for_timestamp">
       <code class="literal">
        explicit_defaults_for_timestamp
       </code>
      </a>
      system variable at server startup.
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       <a class="link" href="server-system-variables.html#sysvar_explicit_defaults_for_timestamp">
        <code class="literal">
         explicit_defaults_for_timestamp
        </code>
       </a>
       is itself deprecated because its only purpose is to permit
            control over deprecated
       <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
        <code class="literal">
         TIMESTAMP
        </code>
       </a>
       behaviors that are
            to be removed in a future MySQL release. When removal of
            those behaviors occurs, expect
       <a class="link" href="server-system-variables.html#sysvar_explicit_defaults_for_timestamp">
        <code class="literal">
         explicit_defaults_for_timestamp
        </code>
       </a>
       to be removed as well.
      </p>
     </div>
     <p>
      For additional information, see
      <a class="xref" href="timestamp-initialization.html" title="13.2.5 Automatic Initialization and Updating for TIMESTAMP and DATETIME">
       Section 13.2.5, “Automatic Initialization and Updating for TIMESTAMP and DATETIME”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_external_user">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_external_user">
       <code class="literal">
        external_user
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275762800">
     </a>
     <a class="indexterm" name="idm46045275761712">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for external_user">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_external_user">
            external_user
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The external user name used during the authentication process,
          as set by the plugin used to authenticate the client. With
          native (built-in) MySQL authentication, or if the plugin does
          not set the value, this variable is
      <code class="literal">
       NULL
      </code>
      .
          See
      <a class="xref" href="proxy-users.html" title="8.2.19 Proxy Users">
       Section 8.2.19, “Proxy Users”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_flush">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_flush">
       <code class="literal">
        flush
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275740544">
     </a>
     <a class="indexterm" name="idm46045275739472">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for flush">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --flush[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_flush">
            flush
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If
      <code class="literal">
       ON
      </code>
      , the server flushes (synchronizes)
          all changes to disk after each SQL statement. Normally, MySQL
          does a write of all changes to disk only after each SQL
          statement and lets the operating system handle the
          synchronizing to disk. See
      <a class="xref" href="crashing.html" title="B.3.3.3 What to Do If MySQL Keeps Crashing">
       Section B.3.3.3, “What to Do If MySQL Keeps Crashing”
      </a>
      . This
          variable is set to
      <code class="literal">
       ON
      </code>
      if you start
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      with the
      <a class="link" href="server-options.html#option_mysqld_flush">
       <code class="option">
        --flush
       </code>
      </a>
      option.
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       If
       <a class="link" href="server-system-variables.html#sysvar_flush">
        <code class="literal">
         flush
        </code>
       </a>
       is enabled, the
            value of
       <a class="link" href="server-system-variables.html#sysvar_flush_time">
        <code class="literal">
         flush_time
        </code>
       </a>
       does
            not matter and changes to
       <a class="link" href="server-system-variables.html#sysvar_flush_time">
        <code class="literal">
         flush_time
        </code>
       </a>
       have no effect
            on flush behavior.
      </p>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_flush_time">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_flush_time">
       <code class="literal">
        flush_time
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275706016">
     </a>
     <a class="indexterm" name="idm46045275704928">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for flush_time">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --flush-time=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_flush_time">
            flush_time
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If this is set to a nonzero value, all tables are closed every
      <a class="link" href="server-system-variables.html#sysvar_flush_time">
       <code class="literal">
        flush_time
       </code>
      </a>
      seconds to free up
          resources and synchronize unflushed data to disk. This option
          is best used only on systems with minimal resources.
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       If
       <a class="link" href="server-system-variables.html#sysvar_flush">
        <code class="literal">
         flush
        </code>
       </a>
       is enabled, the
            value of
       <a class="link" href="server-system-variables.html#sysvar_flush_time">
        <code class="literal">
         flush_time
        </code>
       </a>
       does
            not matter and changes to
       <a class="link" href="server-system-variables.html#sysvar_flush_time">
        <code class="literal">
         flush_time
        </code>
       </a>
       have no effect
            on flush behavior.
      </p>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_foreign_key_checks">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_foreign_key_checks">
       <code class="literal">
        foreign_key_checks
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275667520">
     </a>
     <a class="indexterm" name="idm46045275666480">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for foreign_key_checks">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_foreign_key_checks">
            foreign_key_checks
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If set to 1 (the default), foreign key constraints are
          checked. If set to 0, foreign key constraints are ignored,
          with a couple of exceptions. When re-creating a table that was
          dropped, an error is returned if the table definition does not
          conform to the foreign key constraints referencing the table.
          Likewise, an
      <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       <code class="literal">
        ALTER TABLE
       </code>
      </a>
      operation returns an error if a foreign key definition is
          incorrectly formed. For more information, see
      <a class="xref" href="create-table-foreign-keys.html" title="15.1.20.5 FOREIGN KEY Constraints">
       Section 15.1.20.5, “FOREIGN KEY Constraints”
      </a>
      .
     </p>
     <p>
      Setting this variable has the same effect on
      <a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
       <code class="literal">
        NDB
       </code>
      </a>
      tables as it does for
      <code class="literal">
       InnoDB
      </code>
      tables. Typically you leave this
          setting enabled during normal operation, to enforce
      <a class="link" href="glossary.html#glos_referential_integrity" title="referential integrity">
       referential
          integrity
      </a>
      . Disabling foreign key checking can be useful
          for reloading
      <code class="literal">
       InnoDB
      </code>
      tables in an order
          different from that required by their parent/child
          relationships. See
      <a class="xref" href="create-table-foreign-keys.html" title="15.1.20.5 FOREIGN KEY Constraints">
       Section 15.1.20.5, “FOREIGN KEY Constraints”
      </a>
      .
     </p>
     <p>
      Setting
      <code class="literal">
       foreign_key_checks
      </code>
      to 0 also
          affects data definition statements:
      <a class="link" href="drop-database.html" title="15.1.24 DROP DATABASE Statement">
       <code class="literal">
        DROP
          SCHEMA
       </code>
      </a>
      drops a schema even if it contains tables
          that have foreign keys that are referred to by tables outside
          the schema, and
      <a class="link" href="drop-table.html" title="15.1.32 DROP TABLE Statement">
       <code class="literal">
        DROP TABLE
       </code>
      </a>
      drops tables that have foreign keys that are referred to by
          other tables.
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       Setting
       <code class="literal">
        foreign_key_checks
       </code>
       to 1 does not
            trigger a scan of the existing table data. Therefore, rows
            added to the table while
       <a class="link" href="server-system-variables.html#sysvar_foreign_key_checks">
        <code class="literal">
         foreign_key_checks = 0
        </code>
       </a>
       are
            not verified for consistency.
      </p>
      <p>
       Dropping an index required by a foreign key constraint is
            not permitted, even with
       <a class="link" href="server-system-variables.html#sysvar_foreign_key_checks">
        <code class="literal">
         foreign_key_checks=0
        </code>
       </a>
       . The
            foreign key constraint must be removed before dropping the
            index.
      </p>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ft_boolean_syntax">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ft_boolean_syntax">
       <code class="literal">
        ft_boolean_syntax
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275628272">
     </a>
     <a class="indexterm" name="idm46045275627232">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ft_boolean_syntax">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ft-boolean-syntax=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ft_boolean_syntax">
            ft_boolean_syntax
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           + -&gt;&lt;()~*:""&amp;|
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The list of operators supported by boolean full-text searches
          performed using
      <code class="literal">
       IN BOOLEAN MODE
      </code>
      . See
      <a class="xref" href="fulltext-boolean.html" title="14.9.2 Boolean Full-Text Searches">
       Section 14.9.2, “Boolean Full-Text Searches”
      </a>
      .
     </p>
     <p>
      The default variable value is
      <code class="literal">
       '+ -&gt;&lt;()~*:""&amp;|'
      </code>
      . The rules
          for changing the value are as follows:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         Operator function is determined by position within the
              string.
        </p>
       </li>
       <li class="listitem">
        <p>
         The replacement value must be 14 characters.
        </p>
       </li>
       <li class="listitem">
        <p>
         Each character must be an ASCII nonalphanumeric character.
        </p>
       </li>
       <li class="listitem">
        <p>
         Either the first or second character must be a space.
        </p>
       </li>
       <li class="listitem">
        <p>
         No duplicates are permitted except the phrase quoting
              operators in positions 11 and 12. These two characters are
              not required to be the same, but they are the only two
              that may be.
        </p>
       </li>
       <li class="listitem">
        <p>
         Positions 10, 13, and 14 (which by default are set to
         <code class="literal">
          :
         </code>
         ,
         <code class="literal">
          &amp;
         </code>
         , and
         <code class="literal">
          |
         </code>
         ) are reserved for future extensions.
        </p>
       </li>
      </ul>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ft_max_word_len">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ft_max_word_len">
       <code class="literal">
        ft_max_word_len
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275591984">
     </a>
     <a class="indexterm" name="idm46045275590896">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ft_max_word_len">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ft-max-word-len=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ft_max_word_len">
            ft_max_word_len
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           84
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           10
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           84
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum length of the word to be included in a
      <code class="literal">
       MyISAM
      </code>
      <code class="literal">
       FULLTEXT
      </code>
      index.
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       <code class="literal">
        FULLTEXT
       </code>
       indexes on
       <code class="literal">
        MyISAM
       </code>
       tables must be rebuilt after
            changing this variable. Use
       <code class="literal">
        REPAIR TABLE
        <em class="replaceable">
         <code>
          tbl_name
         </code>
        </em>
        QUICK
       </code>
       .
      </p>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ft_min_word_len">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ft_min_word_len">
       <code class="literal">
        ft_min_word_len
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275556752">
     </a>
     <a class="indexterm" name="idm46045275555664">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ft_min_word_len">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ft-min-word-len=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ft_min_word_len">
            ft_min_word_len
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           4
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           82
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The minimum length of the word to be included in a
      <code class="literal">
       MyISAM
      </code>
      <code class="literal">
       FULLTEXT
      </code>
      index.
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       <code class="literal">
        FULLTEXT
       </code>
       indexes on
       <code class="literal">
        MyISAM
       </code>
       tables must be rebuilt after
            changing this variable. Use
       <code class="literal">
        REPAIR TABLE
        <em class="replaceable">
         <code>
          tbl_name
         </code>
        </em>
        QUICK
       </code>
       .
      </p>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ft_query_expansion_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ft_query_expansion_limit">
       <code class="literal">
        ft_query_expansion_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275521440">
     </a>
     <a class="indexterm" name="idm46045275520336">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ft_query_expansion_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ft-query-expansion-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ft_query_expansion_limit">
            ft_query_expansion_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           20
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           1000
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of top matches to use for full-text searches
          performed using
      <code class="literal">
       WITH QUERY EXPANSION
      </code>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ft_stopword_file">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ft_stopword_file">
       <code class="literal">
        ft_stopword_file
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275490192">
     </a>
     <a class="indexterm" name="idm46045275489104">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ft_stopword_file">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ft-stopword-file=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ft_stopword_file">
            ft_stopword_file
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The file from which to read the list of stopwords for
          full-text searches on
      <code class="literal">
       MyISAM
      </code>
      tables. The
          server looks for the file in the data directory unless an
          absolute path name is given to specify a different directory.
          All the words from the file are used; comments are
      <span class="emphasis">
       <em>
        not
       </em>
      </span>
      honored. By default, a built-in list
          of stopwords is used (as defined in the
      <code class="filename">
       storage/myisam/ft_static.c
      </code>
      file). Setting
          this variable to the empty string (
      <code class="literal">
       ''
      </code>
      )
          disables stopword filtering. See also
      <a class="xref" href="fulltext-stopwords.html" title="14.9.4 Full-Text Stopwords">
       Section 14.9.4, “Full-Text Stopwords”
      </a>
      .
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       <code class="literal">
        FULLTEXT
       </code>
       indexes on
       <code class="literal">
        MyISAM
       </code>
       tables must be rebuilt after
            changing this variable or the contents of the stopword file.
            Use
       <code class="literal">
        REPAIR TABLE
        <em class="replaceable">
         <code>
          tbl_name
         </code>
        </em>
        QUICK
       </code>
       .
      </p>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_general_log">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_general_log">
       <code class="literal">
        general_log
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275459792">
     </a>
     <a class="indexterm" name="idm46045275458704">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for general_log">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --general-log[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_general_log">
            general_log
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether the general query log is enabled. The value can be 0
          (or
      <code class="literal">
       OFF
      </code>
      ) to disable the log or 1 (or
      <code class="literal">
       ON
      </code>
      ) to enable the log. The destination for
          log output is controlled by the
      <a class="link" href="server-system-variables.html#sysvar_log_output">
       <code class="literal">
        log_output
       </code>
      </a>
      system variable;
          if that value is
      <code class="literal">
       NONE
      </code>
      , no log entries are
          written even if the log is enabled.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_general_log_file">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_general_log_file">
       <code class="literal">
        general_log_file
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275430688">
     </a>
     <a class="indexterm" name="idm46045275429600">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for general_log_file">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --general-log-file=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_general_log_file">
            general_log_file
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           host_name.log
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The name of the general query log file. The default value is
      <code class="filename">
       <em class="replaceable">
        <code>
         host_name
        </code>
       </em>
       .log
      </code>
      ,
          but the initial value can be changed with the
      <a class="link" href="server-system-variables.html#sysvar_general_log_file">
       <code class="option">
        --general_log_file
       </code>
      </a>
      option.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_generated_random_password_length">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_generated_random_password_length">
       <code class="literal">
        generated_random_password_length
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275403056">
     </a>
     <a class="indexterm" name="idm46045275401952">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for generated_random_password_length">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --generated-random-password-length=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_generated_random_password_length">
            generated_random_password_length
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           20
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           5
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           255
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum number of characters permitted in random passwords
          generated for
      <a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
       <code class="literal">
        CREATE USER
       </code>
      </a>
      ,
      <a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
       <code class="literal">
        ALTER USER
       </code>
      </a>
      , and
      <a class="link" href="set-password.html" title="15.7.1.10 SET PASSWORD Statement">
       <code class="literal">
        SET PASSWORD
       </code>
      </a>
      statements. For
          more information, see
      <a class="xref" href="password-management.html#random-password-generation" title="Random Password Generation">
       Random Password Generation
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_global_connection_memory_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_global_connection_memory_limit">
       <code class="literal">
        global_connection_memory_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275367744">
     </a>
     <a class="indexterm" name="idm46045275366640">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for global_connection_memory_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --global-connection-memory-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_global_connection_memory_limit">
            global_connection_memory_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           16777216
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Set the total amount of memory that can be used by all user
          connections; that is,
      <a class="link" href="server-status-variables.html#statvar_Global_connection_memory">
       <code class="literal">
        Global_connection_memory
       </code>
      </a>
      should not exceed this amount. Any time that it does, all
          queries (including any currently running) from regular users
          are rejected with
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_global_conn_limit" target="_top">
       <code class="literal">
        ER_GLOBAL_CONN_LIMIT
       </code>
      </a>
      .
     </p>
     <p>
      Memory used by the system users such as the MySQL root user is
          included in this total, but is not counted towards the
          disconnection limit; such users are never disconnected due to
          memory usage.
     </p>
     <p>
      Memory used by the
      <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
       <code class="literal">
        InnoDB
       </code>
      </a>
      buffer
          pool is excluded from the total.
     </p>
     <p>
      You must have the
      <a class="link" href="privileges-provided.html#priv_system-variables-admin">
       <code class="literal">
        SYSTEM_VARIABLES_ADMIN
       </code>
      </a>
      or
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege to set this
          variable.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_global_connection_memory_tracking">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_global_connection_memory_tracking">
       <code class="literal">
        global_connection_memory_tracking
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275326976">
     </a>
     <a class="indexterm" name="idm46045275325936">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for global_connection_memory_tracking">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --global-connection-memory-tracking={TRUE|FALSE}
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_global_connection_memory_tracking">
            global_connection_memory_tracking
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           FALSE
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Determines whether the server calculates
      <a class="link" href="server-status-variables.html#statvar_Global_connection_memory">
       <code class="literal">
        Global_connection_memory
       </code>
      </a>
      .
          This variable must be enabled explicitly; otherwise, the
          memory calculation is not performed, and
      <code class="literal">
       Global_connection_memory
      </code>
      is not set.
     </p>
     <p>
      You must have the
      <a class="link" href="privileges-provided.html#priv_system-variables-admin">
       <code class="literal">
        SYSTEM_VARIABLES_ADMIN
       </code>
      </a>
      or
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege to set this
          variable.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_group_concat_max_len">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_group_concat_max_len">
       <code class="literal">
        group_concat_max_len
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275296176">
     </a>
     <a class="indexterm" name="idm46045275295136">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for group_concat_max_len">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --group-concat-max-len=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_group_concat_max_len">
            group_concat_max_len
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           4
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum permitted result length in bytes for the
      <a class="link" href="aggregate-functions.html#function_group-concat">
       <code class="literal">
        GROUP_CONCAT()
       </code>
      </a>
      function. The
          default is 1024.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_have_compress">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_have_compress">
       <code class="literal">
        have_compress
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275261984">
     </a>
     <a class="indexterm" name="idm46045275260896">
     </a>
     <p>
      <code class="literal">
       YES
      </code>
      if the
      <code class="literal">
       zlib
      </code>
      compression library is available to the server,
      <code class="literal">
       NO
      </code>
      if not. If not, the
      <a class="link" href="encryption-functions.html#function_compress">
       <code class="literal">
        COMPRESS()
       </code>
      </a>
      and
      <a class="link" href="encryption-functions.html#function_uncompress">
       <code class="literal">
        UNCOMPRESS()
       </code>
      </a>
      functions cannot
          be used.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_have_dynamic_loading">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_have_dynamic_loading">
       <code class="literal">
        have_dynamic_loading
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275251872">
     </a>
     <a class="indexterm" name="idm46045275250832">
     </a>
     <p>
      <code class="literal">
       YES
      </code>
      if
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      supports
          dynamic loading of plugins,
      <code class="literal">
       NO
      </code>
      if not. If
          the value is
      <code class="literal">
       NO
      </code>
      , you cannot use options
          such as
      <a class="link" href="server-options.html#option_mysqld_plugin-load">
       <code class="option">
        --plugin-load
       </code>
      </a>
      to load
          plugins at server startup, or the
      <a class="link" href="install-plugin.html" title="15.7.4.4 INSTALL PLUGIN Statement">
       <code class="literal">
        INSTALL
          PLUGIN
       </code>
      </a>
      statement to load plugins at runtime.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_have_geometry">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_have_geometry">
       <code class="literal">
        have_geometry
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275240880">
     </a>
     <a class="indexterm" name="idm46045275239792">
     </a>
     <p>
      <code class="literal">
       YES
      </code>
      if the server supports spatial data
          types,
      <code class="literal">
       NO
      </code>
      if not.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_have_profiling">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_have_profiling">
       <code class="literal">
        have_profiling
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275234112">
     </a>
     <a class="indexterm" name="idm46045275233024">
     </a>
     <p>
      <code class="literal">
       YES
      </code>
      if statement profiling capability is
          present,
      <code class="literal">
       NO
      </code>
      if not. If present, the
      <code class="literal">
       profiling
      </code>
      system variable controls whether
          this capability is enabled or disabled. See
      <a class="xref" href="show-profiles.html" title="15.7.7.33 SHOW PROFILES Statement">
       Section 15.7.7.33, “SHOW PROFILES Statement”
      </a>
      .
     </p>
     <p>
      This variable is deprecated; you should expect it to be
          removed in a future MySQL release.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_have_query_cache">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_have_query_cache">
       <code class="literal">
        have_query_cache
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275225312">
     </a>
     <a class="indexterm" name="idm46045275224224">
     </a>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_have_query_cache">
       <code class="literal">
        have_query_cache
       </code>
      </a>
      is
          deprecated, always has a value of
      <code class="literal">
       NO
      </code>
      , and
          you should expect it to be removed in a future MySQL release.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_have_rtree_keys">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_have_rtree_keys">
       <code class="literal">
        have_rtree_keys
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275217936">
     </a>
     <a class="indexterm" name="idm46045275216848">
     </a>
     <p>
      <code class="literal">
       YES
      </code>
      if
      <code class="literal">
       RTREE
      </code>
      indexes are
          available,
      <code class="literal">
       NO
      </code>
      if not. (These are used for
          spatial indexes in
      <code class="literal">
       MyISAM
      </code>
      tables.)
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_have_statement_timeout">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_have_statement_timeout">
       <code class="literal">
        have_statement_timeout
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275209648">
     </a>
     <a class="indexterm" name="idm46045275208608">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for have_statement_timeout">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_have_statement_timeout">
            have_statement_timeout
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether the statement execution timeout feature is available
          (see
      <a class="xref" href="optimizer-hints.html#optimizer-hints-execution-time" title="Statement Execution Time Optimizer Hints">
       Statement Execution Time Optimizer Hints
      </a>
      ). The
          value can be
      <code class="literal">
       NO
      </code>
      if the background thread
          used by this feature could not be initialized.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_have_symlink">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_have_symlink">
       <code class="literal">
        have_symlink
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275187360">
     </a>
     <a class="indexterm" name="idm46045275186272">
     </a>
     <p>
      <code class="literal">
       YES
      </code>
      if symbolic link support is enabled,
      <code class="literal">
       NO
      </code>
      if not. This is required on Unix for
          support of the
      <code class="literal">
       DATA DIRECTORY
      </code>
      and
      <code class="literal">
       INDEX DIRECTORY
      </code>
      table options. If the
          server is started with the
      <a class="link" href="server-options.html#option_mysqld_symbolic-links">
       <code class="option">
        --skip-symbolic-links
       </code>
      </a>
      option, the value is
      <code class="literal">
       DISABLED
      </code>
      .
     </p>
     <p>
      This variable has no meaning on Windows.
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       Symbolic link support, along with the
       <a class="link" href="server-options.html#option_mysqld_symbolic-links">
        <code class="option">
         --symbolic-links
        </code>
       </a>
       option that
            controls it, is deprecated; expect these to be removed in a
            future version of MySQL. In addition, the option is disabled
            by default. The related
       <a class="link" href="server-system-variables.html#sysvar_have_symlink">
        <code class="literal">
         have_symlink
        </code>
       </a>
       system
            variable also is deprecated and you should expect it to be
            removed in a future version of MySQL.
      </p>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_histogram_generation_max_mem_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_histogram_generation_max_mem_size">
       <code class="literal">
        histogram_generation_max_mem_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275173328">
     </a>
     <a class="indexterm" name="idm46045275172288">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for histogram_generation_max_mem_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --histogram-generation-max-mem-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_histogram_generation_max_mem_size">
            histogram_generation_max_mem_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           20000000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1000000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum amount of memory available for generating
          histogram statistics. See
      <a class="xref" href="optimizer-statistics.html" title="10.9.6 Optimizer Statistics">
       Section 10.9.6, “Optimizer Statistics”
      </a>
      , and
      <a class="xref" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
       Section 15.7.3.1, “ANALYZE TABLE Statement”
      </a>
      .
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_host_cache_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_host_cache_size">
       <code class="literal">
        host_cache_size
       </code>
      </a>
     </p>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for host_cache_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --host-cache-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_host_cache_size">
            host_cache_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           -1
          </code>
          (signifies autosizing; do not assign this literal value)
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           65536
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The MySQL server maintains an in-memory host cache that
          contains client host name and IP address information and is
          used to avoid Domain Name System (DNS) lookups; see
      <a class="xref" href="host-cache.html" title="7.1.12.3 DNS Lookups and the Host Cache">
       Section 7.1.12.3, “DNS Lookups and the Host Cache”
      </a>
      .
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_host_cache_size">
       <code class="literal">
        host_cache_size
       </code>
      </a>
      variable
          controls the size of the host cache, as well as the size of
          the Performance Schema
      <a class="link" href="performance-schema-host-cache-table.html" title="29.12.22.3 The host_cache Table">
       <code class="literal">
        host_cache
       </code>
      </a>
      table that exposes the cache contents. Setting
      <a class="link" href="server-system-variables.html#sysvar_host_cache_size">
       <code class="literal">
        host_cache_size
       </code>
      </a>
      has these
          effects:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         Setting the size to 0 disables the host cache. With the
              cache disabled, the server performs a DNS lookup every
              time a client connects.
        </p>
       </li>
       <li class="listitem">
        <p>
         Changing the size at runtime causes an implicit host cache
              flushing operation that clears the host cache, truncates
              the
         <a class="link" href="performance-schema-host-cache-table.html" title="29.12.22.3 The host_cache Table">
          <code class="literal">
           host_cache
          </code>
         </a>
         table, and
              unblocks any blocked hosts.
        </p>
       </li>
      </ul>
     </div>
     <p>
      The default value is autosized to 128, plus 1 for a value of
      <a class="link" href="server-system-variables.html#sysvar_max_connections">
       <code class="literal">
        max_connections
       </code>
      </a>
      up to 500,
          plus 1 for every increment of 20 over 500 in the
      <a class="link" href="server-system-variables.html#sysvar_max_connections">
       <code class="literal">
        max_connections
       </code>
      </a>
      value, capped
          to a limit of 2000.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_hostname">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_hostname">
       <code class="literal">
        hostname
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275095696">
     </a>
     <a class="indexterm" name="idm46045275094608">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for hostname">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_hostname">
            hostname
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The server sets this variable to the server host name at
          startup. The maximum length is 255 characters.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_identity">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_identity">
       <code class="literal">
        identity
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275075040">
     </a>
     <a class="indexterm" name="idm46045275073952">
     </a>
     <p>
      This variable is a synonym for the
      <a class="link" href="server-system-variables.html#sysvar_last_insert_id">
       <code class="literal">
        last_insert_id
       </code>
      </a>
      variable. It
          exists for compatibility with other database systems. You can
          read its value with
      <code class="literal">
       SELECT @@identity
      </code>
      , and
          set it using
      <code class="literal">
       SET identity
      </code>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_init_connect">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_init_connect">
       <code class="literal">
        init_connect
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275066880">
     </a>
     <a class="indexterm" name="idm46045275065792">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for init_connect">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --init-connect=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_init_connect">
            init_connect
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      A string to be executed by the server for each client that
          connects. The string consists of one or more SQL statements,
          separated by semicolon characters.
     </p>
     <p>
      For users that have the
      <a class="link" href="privileges-provided.html#priv_connection-admin">
       <code class="literal">
        CONNECTION_ADMIN
       </code>
      </a>
      privilege (or
          the deprecated
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege), the content of
      <a class="link" href="server-system-variables.html#sysvar_init_connect">
       <code class="literal">
        init_connect
       </code>
      </a>
      is not executed.
          This is done so that an erroneous value for
      <a class="link" href="server-system-variables.html#sysvar_init_connect">
       <code class="literal">
        init_connect
       </code>
      </a>
      does not prevent
          all clients from connecting. For example, the value might
          contain a statement that has a syntax error, thus causing
          client connections to fail. Not executing
      <a class="link" href="server-system-variables.html#sysvar_init_connect">
       <code class="literal">
        init_connect
       </code>
      </a>
      for users that
          have the
      <a class="link" href="privileges-provided.html#priv_connection-admin">
       <code class="literal">
        CONNECTION_ADMIN
       </code>
      </a>
      or
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege enables them to
          open a connection and fix the
      <a class="link" href="server-system-variables.html#sysvar_init_connect">
       <code class="literal">
        init_connect
       </code>
      </a>
      value.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_init_connect">
       <code class="literal">
        init_connect
       </code>
      </a>
      execution is
          skipped for any client user with an expired password. This is
          done because such a user cannot execute arbitrary statements,
          and thus
      <a class="link" href="server-system-variables.html#sysvar_init_connect">
       <code class="literal">
        init_connect
       </code>
      </a>
      execution fails, leaving the client unable to connect.
          Skipping
      <a class="link" href="server-system-variables.html#sysvar_init_connect">
       <code class="literal">
        init_connect
       </code>
      </a>
      execution enables the user to connect and change password.
     </p>
     <p>
      The server discards any result sets produced by statements in
          the value of
      <a class="link" href="server-system-variables.html#sysvar_init_connect">
       <code class="literal">
        init_connect
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_information_schema_stats_expiry">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
       <code class="literal">
        information_schema_stats_expiry
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045275026736">
     </a>
     <a class="indexterm" name="idm46045275025632">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for information_schema_stats_expiry">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --information-schema-stats-expiry=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
            information_schema_stats_expiry
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           86400
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Some
      <code class="literal">
       INFORMATION_SCHEMA
      </code>
      tables contain
          columns that provide table statistics:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-none"><div class="docs-select-all right" id="sa46338806"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">STATISTICS.CARDINALITY
TABLES.AUTO_INCREMENT
TABLES.AVG_ROW_LENGTH
TABLES.CHECKSUM
TABLES.CHECK_TIME
TABLES.CREATE_TIME
TABLES.DATA_FREE
TABLES.DATA_LENGTH
TABLES.INDEX_LENGTH
TABLES.MAX_DATA_LENGTH
TABLES.TABLE_ROWS
TABLES.UPDATE_TIME</code></pre>
     </div>
     <p>
      Those columns represent dynamic table metadata; that is,
          information that changes as table contents change.
     </p>
     <p>
      By default, MySQL retrieves cached values for those columns
          from the
      <code class="literal">
       mysql.index_stats
      </code>
      and
      <code class="literal">
       mysql.table_stats
      </code>
      dictionary tables when
          the columns are queried, which is more efficient than
          retrieving statistics directly from the storage engine. If
          cached statistics are not available or have expired, MySQL
          retrieves the latest statistics from the storage engine and
          caches them in the
      <code class="literal">
       mysql.index_stats
      </code>
      and
      <code class="literal">
       mysql.table_stats
      </code>
      dictionary tables.
          Subsequent queries retrieve the cached statistics until the
          cached statistics expire. A server restart or the first
          opening of the
      <code class="literal">
       mysql.index_stats
      </code>
      and
      <code class="literal">
       mysql.table_stats
      </code>
      tables do not update
          cached statistics automatically.
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
       <code class="literal">
        information_schema_stats_expiry
       </code>
      </a>
      session variable defines the period of time before cached
          statistics expire. The default is 86400 seconds (24 hours),
          but the time period can be extended to as much as one year.
     </p>
     <p>
      To update cached values at any time for a given table, use
      <a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
       <code class="literal">
        ANALYZE TABLE
       </code>
      </a>
      .
     </p>
     <p>
      To always retrieve the latest statistics directly from the
          storage engine and bypass cached values, set
      <a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
       <code class="literal">
        information_schema_stats_expiry
       </code>
      </a>
      to
      <code class="literal">
       0
      </code>
      .
     </p>
     <p>
      Querying statistics columns does not store or update
          statistics in the
      <code class="literal">
       mysql.index_stats
      </code>
      and
      <code class="literal">
       mysql.table_stats
      </code>
      dictionary tables under
          these circumstances:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         When cached statistics have not expired.
        </p>
       </li>
       <li class="listitem">
        <p>
         When
         <a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
          <code class="literal">
           information_schema_stats_expiry
          </code>
         </a>
         is set to 0.
        </p>
       </li>
       <li class="listitem">
        <p>
         When the server is in
         <a class="link" href="server-system-variables.html#sysvar_read_only">
          <code class="literal">
           read_only
          </code>
         </a>
         ,
         <a class="link" href="server-system-variables.html#sysvar_super_read_only">
          <code class="literal">
           super_read_only
          </code>
         </a>
         ,
         <a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
          <code class="literal">
           transaction_read_only
          </code>
         </a>
         , or
         <a class="link" href="innodb-parameters.html#sysvar_innodb_read_only">
          <code class="literal">
           innodb_read_only
          </code>
         </a>
         mode.
        </p>
       </li>
       <li class="listitem">
        <p>
         When the query also fetches Performance Schema data.
        </p>
       </li>
      </ul>
     </div>
     <p>
      The statistics cache may be updated during a
          multiple-statement transaction before it is known whether the
          transaction commits. As a result, the cache may contain
          information that does not correspond to a known committed
          state. This can occur with
      <a class="link" href="server-system-variables.html#sysvar_autocommit">
       <code class="literal">
        autocommit=0
       </code>
      </a>
      or after
      <a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
       <code class="literal">
        START
          TRANSACTION
       </code>
      </a>
      .
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
       <code class="literal">
        information_schema_stats_expiry
       </code>
      </a>
      is a session variable, and each client session can define its
          own expiration value. Statistics that are retrieved from the
          storage engine and cached by one session are available to
          other sessions.
     </p>
     <p>
      For related information, see
      <a class="xref" href="information-schema-optimization.html" title="10.2.3 Optimizing INFORMATION_SCHEMA Queries">
       Section 10.2.3, “Optimizing INFORMATION_SCHEMA Queries”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_init_file">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_init_file">
       <code class="literal">
        init_file
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274961120">
     </a>
     <a class="indexterm" name="idm46045274960032">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for init_file">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --init-file=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_init_file">
            init_file
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If specified, this variable names a file containing SQL
          statements to be read and executed during the startup process.
          The acceptable format for statements in this file support the
          following constructs:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          delimiter ;
         </code>
         , to set the statement
              delimiter to the
         <code class="literal">
          ;
         </code>
         character.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          delimiter $$
         </code>
         , to set the statement
              delimiter to the
         <code class="literal">
          $$
         </code>
         character sequence.
        </p>
       </li>
       <li class="listitem">
        <p>
         Multiple statements on the same line, delimited by the
              current delimiter.
        </p>
       </li>
       <li class="listitem">
        <p>
         Multiple-line statements.
        </p>
       </li>
       <li class="listitem">
        <p>
         Comments from a
         <code class="literal">
          #
         </code>
         character to the end
              of the line.
        </p>
       </li>
       <li class="listitem">
        <p>
         Comments from a
         <code class="literal">
          --
         </code>
         sequence to
              the end of the line.
        </p>
       </li>
       <li class="listitem">
        <p>
         C-style comments from a
         <code class="literal">
          /*
         </code>
         sequence to
              the following
         <code class="literal">
          */
         </code>
         sequence, including
              over multiple lines.
        </p>
       </li>
       <li class="listitem">
        <p>
         Multiple-line string literals enclosed within either
              single quote (
         <code class="literal">
          '
         </code>
         ) or double quote
              (
         <code class="literal">
          "
         </code>
         ) characters.
        </p>
       </li>
      </ul>
     </div>
     <p>
      If the server is started with the
      <a class="link" href="server-options.html#option_mysqld_initialize">
       <code class="option">
        --initialize
       </code>
      </a>
      or
      <a class="link" href="server-options.html#option_mysqld_initialize-insecure">
       <code class="option">
        --initialize-insecure
       </code>
      </a>
      option,
          it operates in bootstrap mode and some functionality is
          unavailable that limits the statements permitted in the file.
          These include statements that relate to account management
          (such as
      <a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
       <code class="literal">
        CREATE USER
       </code>
      </a>
      or
      <a class="link" href="grant.html" title="15.7.1.6 GRANT Statement">
       <code class="literal">
        GRANT
       </code>
      </a>
      ), replication, and global
          transaction identifiers. See
      <a class="xref" href="replication-gtids.html" title="19.1.3 Replication with Global Transaction Identifiers">
       Section 19.1.3, “Replication with Global Transaction Identifiers”
      </a>
      .
     </p>
     <p>
      Threads created during server startup are used for tasks such
          as creating the data dictionary, running upgrade procedures,
          and creating system tables. To ensure a stable and predictable
          environment, these threads are executed with the server
          built-in defaults for some system variables, such as
      <a class="link" href="server-system-variables.html#sysvar_sql_mode">
       <code class="literal">
        sql_mode
       </code>
      </a>
      ,
      <a class="link" href="server-system-variables.html#sysvar_character_set_server">
       <code class="literal">
        character_set_server
       </code>
      </a>
      ,
      <a class="link" href="server-system-variables.html#sysvar_collation_server">
       <code class="literal">
        collation_server
       </code>
      </a>
      ,
      <a class="link" href="server-system-variables.html#sysvar_completion_type">
       <code class="literal">
        completion_type
       </code>
      </a>
      ,
      <a class="link" href="server-system-variables.html#sysvar_explicit_defaults_for_timestamp">
       <code class="literal">
        explicit_defaults_for_timestamp
       </code>
      </a>
      ,
          and
      <a class="link" href="server-system-variables.html#sysvar_default_table_encryption">
       <code class="literal">
        default_table_encryption
       </code>
      </a>
      .
     </p>
     <p>
      These threads are also used to execute the statements in any
          file specified with
      <a class="link" href="server-system-variables.html#sysvar_init_file">
       <code class="literal">
        init_file
       </code>
      </a>
      when starting the server, so such statements execute with the
          server's built-in default values for those system variables.
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       innodb_
       <em class="replaceable">
        <code>
         xxx
        </code>
       </em>
      </code>
     </p>
     <p>
      <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
       <code class="literal">
        InnoDB
       </code>
      </a>
      system variables are
          listed in
      <a class="xref" href="innodb-parameters.html" title="17.14 InnoDB Startup Options and System Variables">
       Section 17.14, “InnoDB Startup Options and System Variables”
      </a>
      . These variables
          control many aspects of storage, memory use, and I/O patterns
          for
      <code class="literal">
       InnoDB
      </code>
      tables, and are especially
          important now that
      <code class="literal">
       InnoDB
      </code>
      is the default
          storage engine.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_insert_id">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_insert_id">
       <code class="literal">
        insert_id
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274901696">
     </a>
     <a class="indexterm" name="idm46045274900608">
     </a>
     <p>
      The value to be used by the following
      <a class="link" href="insert.html" title="15.2.7 INSERT Statement">
       <code class="literal">
        INSERT
       </code>
      </a>
      or
      <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       <code class="literal">
        ALTER TABLE
       </code>
      </a>
      statement when
          inserting an
      <code class="literal">
       AUTO_INCREMENT
      </code>
      value. This is
          mainly used with the binary log.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_interactive_timeout">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_interactive_timeout">
       <code class="literal">
        interactive_timeout
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274892896">
     </a>
     <a class="indexterm" name="idm46045274891856">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for interactive_timeout">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --interactive-timeout=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_interactive_timeout">
            interactive_timeout
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           28800
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of seconds the server waits for activity on an
          interactive connection before closing it. An interactive
          client is defined as a client that uses the
      <code class="literal">
       CLIENT_INTERACTIVE
      </code>
      option to
      <a class="ulink" href="/doc/c-api/8.4/en/mysql-real-connect.html" target="_top">
       <code class="literal">
        mysql_real_connect()
       </code>
      </a>
      . See also
      <a class="link" href="server-system-variables.html#sysvar_wait_timeout">
       <code class="literal">
        wait_timeout
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_internal_tmp_mem_storage_engine">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_internal_tmp_mem_storage_engine">
       <code class="literal">
        internal_tmp_mem_storage_engine
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274857088">
     </a>
     <a class="indexterm" name="idm46045274855984">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for internal_tmp_mem_storage_engine">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --internal-tmp-mem-storage-engine=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_internal_tmp_mem_storage_engine">
            internal_tmp_mem_storage_engine
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           TempTable
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            MEMORY
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            TempTable
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The storage engine for in-memory internal temporary tables
          (see
      <a class="xref" href="internal-temporary-tables.html" title="10.4.4 Internal Temporary Table Use in MySQL">
       Section 10.4.4, “Internal Temporary Table Use in MySQL”
      </a>
      ). Permitted
          values are
      <code class="literal">
       TempTable
      </code>
      (the default) and
      <code class="literal">
       MEMORY
      </code>
      .
     </p>
     <p>
      The
      <a class="link" href="glossary.html#glos_optimizer" title="optimizer">
       optimizer
      </a>
      uses the
          storage engine defined by
      <a class="link" href="server-system-variables.html#sysvar_internal_tmp_mem_storage_engine">
       <code class="literal">
        internal_tmp_mem_storage_engine
       </code>
      </a>
      for in-memory internal temporary tables.
     </p>
     <p>
      Configuring a session setting for
      <a class="link" href="server-system-variables.html#sysvar_internal_tmp_mem_storage_engine">
       <code class="literal">
        internal_tmp_mem_storage_engine
       </code>
      </a>
      requires the
      <a class="link" href="privileges-provided.html#priv_session-variables-admin">
       <code class="literal">
        SESSION_VARIABLES_ADMIN
       </code>
      </a>
      or
      <a class="link" href="privileges-provided.html#priv_system-variables-admin">
       <code class="literal">
        SYSTEM_VARIABLES_ADMIN
       </code>
      </a>
      privilege.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_join_buffer_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_join_buffer_size">
       <code class="literal">
        join_buffer_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274818272">
     </a>
     <a class="indexterm" name="idm46045274817184">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for join_buffer_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --join-buffer-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_join_buffer_size">
            join_buffer_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           262144
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           128
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Windows)
         </th>
         <td>
          <code class="literal">
           4294967168
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Other, 64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551488
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Other, 32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967168
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           128
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The minimum size of the buffer that is used for plain index
          scans, range index scans, and joins that do not use indexes
          and thus perform full table scans. This variable also controls
          the amount of memory used for hash joins. Normally, the best
          way to get fast joins is to add indexes. Increase the value of
      <a class="link" href="server-system-variables.html#sysvar_join_buffer_size">
       <code class="literal">
        join_buffer_size
       </code>
      </a>
      to get a
          faster full join when adding indexes is not possible. One join
          buffer is allocated for each full join between two tables. For
          a complex join between several tables for which indexes are
          not used, multiple join buffers might be necessary.
     </p>
     <p>
      The default is 256KB. The maximum permissible setting for
      <a class="link" href="server-system-variables.html#sysvar_join_buffer_size">
       <code class="literal">
        join_buffer_size
       </code>
      </a>
      is
          4GB−1. Larger values are permitted for 64-bit platforms
          (except 64-bit Windows, for which large values are truncated
          to 4GB−1 with a warning). The block size is 128, and a
          value that is not an exact multiple of the block size is
          rounded down to the next lower multiple of the block size by
          MySQL Server before storing the value for the system variable.
          The parser allows values up to the maximum unsigned integer
          value for the platform (4294967295 or
          2
      <sup>
       32
      </sup>
      −1 for a 32-bit system,
          18446744073709551615 or 2
      <sup>
       64
      </sup>
      −1
          for a 64-bit system) but the actual maximum is a block size
          lower.
     </p>
     <p>
      Unless a Block Nested-Loop or Batched Key Access algorithm is
          used, there is no gain from setting the buffer larger than
          required to hold each matching row, and all joins allocate at
          least the minimum size, so use caution in setting this
          variable to a large value globally. It is better to keep the
          global setting small and change the session setting to a
          larger value only in sessions that are doing large joins, or
          change the setting on a per-query basis by using a
      <code class="literal">
       SET_VAR
      </code>
      optimizer hint (see
      <a class="xref" href="optimizer-hints.html" title="10.9.3 Optimizer Hints">
       Section 10.9.3, “Optimizer Hints”
      </a>
      ). Memory allocation time can
          cause substantial performance drops if the global size is
          larger than needed by most queries that use it.
     </p>
     <p>
      When Block Nested-Loop is used, a larger join buffer can be
          beneficial up to the point where all required columns from all
          rows in the first table are stored in the join buffer. This
          depends on the query; the optimal size may be smaller than
          holding all rows from the first tables.
     </p>
     <p>
      When Batched Key Access is used, the value of
      <a class="link" href="server-system-variables.html#sysvar_join_buffer_size">
       <code class="literal">
        join_buffer_size
       </code>
      </a>
      defines how
          large the batch of keys is in each request to the storage
          engine. The larger the buffer, the more sequential access is
          made to the right hand table of a join operation, which can
          significantly improve performance.
     </p>
     <p>
      For additional information about join buffering, see
      <a class="xref" href="nested-loop-joins.html" title="10.2.1.7 Nested-Loop Join Algorithms">
       Section 10.2.1.7, “Nested-Loop Join Algorithms”
      </a>
      . For information about
          Batched Key Access, see
      <a class="xref" href="bnl-bka-optimization.html" title="10.2.1.12 Block Nested-Loop and Batched Key Access Joins">
       Section 10.2.1.12, “Block Nested-Loop and Batched Key Access Joins”
      </a>
      . For information about
          hash joins, see
      <a class="xref" href="hash-joins.html" title="10.2.1.4 Hash Join Optimization">
       Section 10.2.1.4, “Hash Join Optimization”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_keep_files_on_create">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_keep_files_on_create">
       <code class="literal">
        keep_files_on_create
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274764176">
     </a>
     <a class="indexterm" name="idm46045274763136">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for keep_files_on_create">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --keep-files-on-create[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_keep_files_on_create">
            keep_files_on_create
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If a
      <code class="literal">
       MyISAM
      </code>
      table is created with no
      <code class="literal">
       DATA DIRECTORY
      </code>
      option, the
      <code class="filename">
       .MYD
      </code>
      file is created in the database
          directory. By default, if
      <code class="literal">
       MyISAM
      </code>
      finds an
          existing
      <code class="filename">
       .MYD
      </code>
      file in this case, it
          overwrites it. The same applies to
      <code class="filename">
       .MYI
      </code>
      files for tables created with no
      <code class="literal">
       INDEX
          DIRECTORY
      </code>
      option. To suppress this behavior, set the
      <a class="link" href="server-system-variables.html#sysvar_keep_files_on_create">
       <code class="literal">
        keep_files_on_create
       </code>
      </a>
      variable
          to
      <code class="literal">
       ON
      </code>
      (1), in which case
      <code class="literal">
       MyISAM
      </code>
      does not overwrite existing files
          and returns an error instead. The default value is
      <code class="literal">
       OFF
      </code>
      (0).
     </p>
     <p>
      If a
      <code class="literal">
       MyISAM
      </code>
      table is created with a
      <code class="literal">
       DATA DIRECTORY
      </code>
      or
      <code class="literal">
       INDEX
          DIRECTORY
      </code>
      option and an existing
      <code class="filename">
       .MYD
      </code>
      or
      <code class="filename">
       .MYI
      </code>
      file is
          found, MyISAM always returns an error. It does not overwrite a
          file in the specified directory.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_key_buffer_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
       <code class="literal">
        key_buffer_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274725856">
     </a>
     <a class="indexterm" name="idm46045274724368">
     </a>
     <a class="indexterm" name="idm46045274723280">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for key_buffer_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --key-buffer-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
            key_buffer_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           8388608
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           OS_PER_PROCESS_LIMIT
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Index blocks for
      <code class="literal">
       MyISAM
      </code>
      tables are buffered
          and are shared by all threads.
      <a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
       <code class="literal">
        key_buffer_size
       </code>
      </a>
      is the size
          of the buffer used for index blocks. The key buffer is also
          known as the key cache.
     </p>
     <p>
      The minimum permissible setting is 0, but you cannot set
      <a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
       <code class="literal">
        key_buffer_size
       </code>
      </a>
      to 0
          dynamically. A setting of 0 drops the key cache, which is not
          permitted at runtime. Setting
      <a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
       <code class="literal">
        key_buffer_size
       </code>
      </a>
      to 0 is
          permitted only at startup, in which case the key cache is not
          initialized. Changing the
      <a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
       <code class="literal">
        key_buffer_size
       </code>
      </a>
      setting at
          runtime from a value of 0 to a permitted non-zero value
          initializes the key cache.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
       <code class="literal">
        key_buffer_size
       </code>
      </a>
      can be
          increased or decreased only in increments or multiples of 4096
          bytes. Increasing or decreasing the setting by a nonconforming
          value produces a warning and truncates the setting to a
          conforming value.
     </p>
     <p>
      The maximum permissible setting for
      <a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
       <code class="literal">
        key_buffer_size
       </code>
      </a>
      is
          4GB−1 on 32-bit platforms. Larger values are permitted
          for 64-bit platforms. The effective maximum size might be
          less, depending on your available physical RAM and per-process
          RAM limits imposed by your operating system or hardware
          platform. The value of this variable indicates the amount of
          memory requested. Internally, the server allocates as much
          memory as possible up to this amount, but the actual
          allocation might be less.
     </p>
     <p>
      You can increase the value to get better index handling for
          all reads and multiple writes; on a system whose primary
          function is to run MySQL using the
      <a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine">
       <code class="literal">
        MyISAM
       </code>
      </a>
      storage engine, 25% of the
          machine's total memory is an acceptable value for this
          variable. However, you should be aware that, if you make the
          value too large (for example, more than 50% of the
          machine's total memory), your system might start to page
          and become extremely slow. This is because MySQL relies on the
          operating system to perform file system caching for data
          reads, so you must leave some room for the file system cache.
          You should also consider the memory requirements of any other
          storage engines that you may be using in addition to
      <a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine">
       <code class="literal">
        MyISAM
       </code>
      </a>
      .
     </p>
     <p>
      For even more speed when writing many rows at the same time,
          use
      <a class="link" href="lock-tables.html" title="15.3.6 LOCK TABLES and UNLOCK TABLES Statements">
       <code class="literal">
        LOCK TABLES
       </code>
      </a>
      . See
      <a class="xref" href="insert-optimization.html" title="10.2.5.1 Optimizing INSERT Statements">
       Section 10.2.5.1, “Optimizing INSERT Statements”
      </a>
      .
     </p>
     <p>
      You can check the performance of the key buffer by issuing a
      <a class="link" href="show-status.html" title="15.7.7.37 SHOW STATUS Statement">
       <code class="literal">
        SHOW STATUS
       </code>
      </a>
      statement and
          examining the
      <a class="link" href="server-status-variables.html#statvar_Key_read_requests">
       <code class="literal">
        Key_read_requests
       </code>
      </a>
      ,
      <a class="link" href="server-status-variables.html#statvar_Key_reads">
       <code class="literal">
        Key_reads
       </code>
      </a>
      ,
      <a class="link" href="server-status-variables.html#statvar_Key_write_requests">
       <code class="literal">
        Key_write_requests
       </code>
      </a>
      , and
      <a class="link" href="server-status-variables.html#statvar_Key_writes">
       <code class="literal">
        Key_writes
       </code>
      </a>
      status variables.
          (See
      <a class="xref" href="show.html" title="15.7.7 SHOW Statements">
       Section 15.7.7, “SHOW Statements”
      </a>
      .) The
      <code class="literal">
       Key_reads/Key_read_requests
      </code>
      ratio should
          normally be less than 0.01. The
      <code class="literal">
       Key_writes/Key_write_requests
      </code>
      ratio is
          usually near 1 if you are using mostly updates and deletes,
          but might be much smaller if you tend to do updates that
          affect many rows at the same time or if you are using the
      <code class="literal">
       DELAY_KEY_WRITE
      </code>
      table option.
     </p>
     <p>
      The fraction of the key buffer in use can be determined using
      <a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
       <code class="literal">
        key_buffer_size
       </code>
      </a>
      in
          conjunction with the
      <a class="link" href="server-status-variables.html#statvar_Key_blocks_unused">
       <code class="literal">
        Key_blocks_unused
       </code>
      </a>
      status
          variable and the buffer block size, which is available from
          the
      <a class="link" href="server-system-variables.html#sysvar_key_cache_block_size">
       <code class="literal">
        key_cache_block_size
       </code>
      </a>
      system variable:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa35017035"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">1 <span class="token operator">-</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>Key_blocks_unused <span class="token operator">*</span> key_cache_block_size<span class="token punctuation">)</span> <span class="token operator">/</span> key_buffer_size<span class="token punctuation">)</span></code></pre>
     </div>
     <p>
      This value is an approximation because some space in the key
          buffer is allocated internally for administrative structures.
          Factors that influence the amount of overhead for these
          structures include block size and pointer size. As block size
          increases, the percentage of the key buffer lost to overhead
          tends to decrease. Larger blocks results in a smaller number
          of read operations (because more keys are obtained per read),
          but conversely an increase in reads of keys that are not
          examined (if not all keys in a block are relevant to a query).
     </p>
     <p>
      It is possible to create multiple
      <code class="literal">
       MyISAM
      </code>
      key caches. The size limit of 4GB applies to each cache
          individually, not as a group. See
      <a class="xref" href="myisam-key-cache.html" title="10.10.2 The MyISAM Key Cache">
       Section 10.10.2, “The MyISAM Key Cache”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_key_cache_age_threshold">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_key_cache_age_threshold">
       <code class="literal">
        key_cache_age_threshold
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274654688">
     </a>
     <a class="indexterm" name="idm46045274653648">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for key_cache_age_threshold">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --key-cache-age-threshold=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_key_cache_age_threshold">
            key_cache_age_threshold
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           300
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           100
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551516
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967196
          </code>
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           100
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This value controls the demotion of buffers from the hot
          sublist of a key cache to the warm sublist. Lower values cause
          demotion to happen more quickly. The minimum value is 100. The
          default value is 300. See
      <a class="xref" href="myisam-key-cache.html" title="10.10.2 The MyISAM Key Cache">
       Section 10.10.2, “The MyISAM Key Cache”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_key_cache_block_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_key_cache_block_size">
       <code class="literal">
        key_cache_block_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274617936">
     </a>
     <a class="indexterm" name="idm46045274616896">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for key_cache_block_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --key-cache-block-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_key_cache_block_size">
            key_cache_block_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           512
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           16384
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           512
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The size in bytes of blocks in the key cache. The default
          value is 1024. See
      <a class="xref" href="myisam-key-cache.html" title="10.10.2 The MyISAM Key Cache">
       Section 10.10.2, “The MyISAM Key Cache”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_key_cache_division_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_key_cache_division_limit">
       <code class="literal">
        key_cache_division_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274581712">
     </a>
     <a class="indexterm" name="idm46045274580608">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for key_cache_division_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --key-cache-division-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_key_cache_division_limit">
            key_cache_division_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           100
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           100
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The division point between the hot and warm sublists of the
          key cache buffer list. The value is the percentage of the
          buffer list to use for the warm sublist. Permissible values
          range from 1 to 100. The default value is 100. See
      <a class="xref" href="myisam-key-cache.html" title="10.10.2 The MyISAM Key Cache">
       Section 10.10.2, “The MyISAM Key Cache”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_large_files_support">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_large_files_support">
       <code class="literal">
        large_files_support
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274550304">
     </a>
     <a class="indexterm" name="idm46045274549264">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for large_files_support">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_large_files_support">
            large_files_support
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      was compiled with options
          for large file support.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_large_pages">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_large_pages">
       <code class="literal">
        large_pages
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274528416">
     </a>
     <a class="indexterm" name="idm46045274527328">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for large-pages">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --large-pages[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_large_pages">
            large_pages
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Platform Specific
         </th>
         <td>
          Linux
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether large page support is enabled (via the
      <a class="link" href="server-options.html#option_mysqld_large-pages">
       <code class="option">
        --large-pages
       </code>
      </a>
      option). See
      <a class="xref" href="large-page-support.html" title="10.12.3.3 Enabling Large Page Support">
       Section 10.12.3.3, “Enabling Large Page Support”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_large_page_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_large_page_size">
       <code class="literal">
        large_page_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274499136">
     </a>
     <a class="indexterm" name="idm46045274498048">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for large_page_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_large_page_size">
            large_page_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           65535
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If large page support is enabled, this shows the size of
          memory pages. Large memory pages are supported only on Linux;
          on other platforms, the value of this variable is always 0.
          See
      <a class="xref" href="large-page-support.html" title="10.12.3.3 Enabling Large Page Support">
       Section 10.12.3.3, “Enabling Large Page Support”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_last_insert_id">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_last_insert_id">
       <code class="literal">
        last_insert_id
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274468368">
     </a>
     <a class="indexterm" name="idm46045274467280">
     </a>
     <p>
      The value to be returned from
      <a class="link" href="information-functions.html#function_last-insert-id">
       <code class="literal">
        LAST_INSERT_ID()
       </code>
      </a>
      . This is
          stored in the binary log when you use
      <a class="link" href="information-functions.html#function_last-insert-id">
       <code class="literal">
        LAST_INSERT_ID()
       </code>
      </a>
      in a statement
          that updates a table. Setting this variable does not update
          the value returned by the
      <a class="ulink" href="/doc/c-api/8.4/en/mysql-insert-id.html" target="_top">
       <code class="literal">
        mysql_insert_id()
       </code>
      </a>
      C API
          function.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_lc_messages">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_lc_messages">
       <code class="literal">
        lc_messages
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274459136">
     </a>
     <a class="indexterm" name="idm46045274458048">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for lc-messages">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --lc-messages=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_lc_messages">
            lc_messages
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           en_US
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The locale to use for error messages. The default is
      <code class="literal">
       en_US
      </code>
      . The server converts the argument to
          a language name and combines it with the value of
      <a class="link" href="server-system-variables.html#sysvar_lc_messages_dir">
       <code class="literal">
        lc_messages_dir
       </code>
      </a>
      to produce
          the location for the error message file. See
      <a class="xref" href="error-message-language.html" title="12.12 Setting the Error Message Language">
       Section 12.12, “Setting the Error Message Language”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_lc_messages_dir">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_lc_messages_dir">
       <code class="literal">
        lc_messages_dir
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274430768">
     </a>
     <a class="indexterm" name="idm46045274429680">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for lc-messages-dir">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --lc-messages-dir=dir_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_lc_messages_dir">
            lc_messages_dir
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Directory name
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The directory where error messages are located. The server
          uses the value together with the value of
      <a class="link" href="server-system-variables.html#sysvar_lc_messages">
       <code class="literal">
        lc_messages
       </code>
      </a>
      to produce the
          location for the error message file. See
      <a class="xref" href="error-message-language.html" title="12.12 Setting the Error Message Language">
       Section 12.12, “Setting the Error Message Language”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_lc_time_names">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_lc_time_names">
       <code class="literal">
        lc_time_names
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274405600">
     </a>
     <a class="indexterm" name="idm46045274404512">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for lc_time_names">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --lc-time-names=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_lc_time_names">
            lc_time_names
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable specifies the locale that controls the language
          used to display day and month names and abbreviations. This
          variable affects the output from the
      <a class="link" href="date-and-time-functions.html#function_date-format">
       <code class="literal">
        DATE_FORMAT()
       </code>
      </a>
      ,
      <a class="link" href="date-and-time-functions.html#function_dayname">
       <code class="literal">
        DAYNAME()
       </code>
      </a>
      and
      <a class="link" href="date-and-time-functions.html#function_monthname">
       <code class="literal">
        MONTHNAME()
       </code>
      </a>
      functions. Locale
          names are POSIX-style values such as
      <code class="literal">
       'ja_JP'
      </code>
      or
      <code class="literal">
       'pt_BR'
      </code>
      . The
          default value is
      <code class="literal">
       'en_US'
      </code>
      regardless of your
          system's locale setting. For further information, see
      <a class="xref" href="locale-support.html" title="12.16 MySQL Server Locale Support">
       Section 12.16, “MySQL Server Locale Support”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_license">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_license">
       <code class="literal">
        license
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274375120">
     </a>
     <a class="indexterm" name="idm46045274374048">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for license">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_license">
            license
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           GPL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The type of license the server has.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_local_infile">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_local_infile">
       <code class="literal">
        local_infile
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274352032">
     </a>
     <a class="indexterm" name="idm46045274350944">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for local_infile">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --local-infile[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_local_infile">
            local_infile
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls server-side
      <code class="literal">
       LOCAL
      </code>
      capability for
      <a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
       <code class="literal">
        LOAD DATA
       </code>
      </a>
      statements. Depending on the
      <a class="link" href="server-system-variables.html#sysvar_local_infile">
       <code class="literal">
        local_infile
       </code>
      </a>
      setting, the
          server refuses or permits local data loading by clients that
          have
      <code class="literal">
       LOCAL
      </code>
      enabled on the client side.
     </p>
     <p>
      To explicitly cause the server to refuse or permit
      <a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
       <code class="literal">
        LOAD DATA
          LOCAL
       </code>
      </a>
      statements (regardless of how client programs
          and libraries are configured at build time or runtime), start
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      with
      <a class="link" href="server-system-variables.html#sysvar_local_infile">
       <code class="literal">
        local_infile
       </code>
      </a>
      disabled or
          enabled, respectively.
      <a class="link" href="server-system-variables.html#sysvar_local_infile">
       <code class="literal">
        local_infile
       </code>
      </a>
      can also be set
          at runtime. For more information, see
      <a class="xref" href="load-data-local-security.html" title="8.1.6 Security Considerations for LOAD DATA LOCAL">
       Section 8.1.6, “Security Considerations for LOAD DATA LOCAL”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_lock_wait_timeout">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_lock_wait_timeout">
       <code class="literal">
        lock_wait_timeout
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274315984">
     </a>
     <a class="indexterm" name="idm46045274314944">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for lock_wait_timeout">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --lock-wait-timeout=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_lock_wait_timeout">
            lock_wait_timeout
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable specifies the timeout in seconds for attempts to
          acquire metadata locks. The permissible values range from 1 to
          31536000 (1 year). The default is 31536000.
     </p>
     <p>
      This timeout applies to all statements that use metadata
          locks. These include DML and DDL operations on tables, views,
          stored procedures, and stored functions, as well as
      <a class="link" href="lock-tables.html" title="15.3.6 LOCK TABLES and UNLOCK TABLES Statements">
       <code class="literal">
        LOCK TABLES
       </code>
      </a>
      ,
      <a class="link" href="flush.html#flush-tables-with-read-lock">
       <code class="literal">
        FLUSH TABLES WITH READ LOCK
       </code>
      </a>
      ,
          and
      <a class="link" href="handler.html" title="15.2.5 HANDLER Statement">
       <code class="literal">
        HANDLER
       </code>
      </a>
      statements.
     </p>
     <p>
      This timeout does not apply to implicit accesses to system
          tables in the
      <code class="literal">
       mysql
      </code>
      database, such as grant
          tables modified by
      <a class="link" href="grant.html" title="15.7.1.6 GRANT Statement">
       <code class="literal">
        GRANT
       </code>
      </a>
      or
      <a class="link" href="revoke.html" title="15.7.1.8 REVOKE Statement">
       <code class="literal">
        REVOKE
       </code>
      </a>
      statements or table
          logging statements. The timeout does apply to system tables
          accessed directly, such as with
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      or
      <a class="link" href="update.html" title="15.2.17 UPDATE Statement">
       <code class="literal">
        UPDATE
       </code>
      </a>
      .
     </p>
     <p>
      The timeout value applies separately for each metadata lock
          attempt. A given statement can require more than one lock, so
          it is possible for the statement to block for longer than the
      <a class="link" href="server-system-variables.html#sysvar_lock_wait_timeout">
       <code class="literal">
        lock_wait_timeout
       </code>
      </a>
      value
          before reporting a timeout error. When lock timeout occurs,
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_lock_wait_timeout" target="_top">
       <code class="literal">
        ER_LOCK_WAIT_TIMEOUT
       </code>
      </a>
      is
          reported.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_lock_wait_timeout">
       <code class="literal">
        lock_wait_timeout
       </code>
      </a>
      also
          defines the amount of time that a
      <a class="link" href="lock-instance-for-backup.html" title="15.3.5 LOCK INSTANCE FOR BACKUP and UNLOCK INSTANCE Statements">
       <code class="literal">
        LOCK
          INSTANCE FOR BACKUP
       </code>
      </a>
      statement waits for a lock
          before giving up.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_locked_in_memory">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_locked_in_memory">
       <code class="literal">
        locked_in_memory
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274266368">
     </a>
     <a class="indexterm" name="idm46045274265280">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for locked_in_memory">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_locked_in_memory">
            locked_in_memory
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      was locked in memory with
      <a class="link" href="server-options.html#option_mysqld_memlock">
       <code class="option">
        --memlock
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_log_error">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_log_error">
       <code class="literal">
        log_error
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274241184">
     </a>
     <a class="indexterm" name="idm46045274240096">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for log-error">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --log-error[=file_name]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_log_error">
            log_error
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The default error log destination. If the destination is the
          console, the value is
      <code class="literal">
       stderr
      </code>
      . Otherwise,
          the destination is a file and the
      <a class="link" href="server-system-variables.html#sysvar_log_error">
       <code class="literal">
        log_error
       </code>
      </a>
      value is the file
          name. See
      <a class="xref" href="error-log.html" title="7.4.2 The Error Log">
       Section 7.4.2, “The Error Log”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_log_error_services">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_log_error_services">
       <code class="literal">
        log_error_services
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274215280">
     </a>
     <a class="indexterm" name="idm46045274214240">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for log_error_services">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --log-error-services=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_log_error_services">
            log_error_services
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           log_filter_internal; log_sink_internal
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The components to enable for error logging. The variable may
          contain a list with 0, 1, or many elements. In the latter
          case, elements may be delimited by semicolons or commas,
          optionally followed by space. A given setting cannot use both
          semicolon and comma separators. Component order is significant
          because the server executes components in the order listed.
     </p>
     <p>
      Any loadable (not built in) component named in
      <a class="link" href="server-system-variables.html#sysvar_log_error_services">
       <code class="literal">
        log_error_services
       </code>
      </a>
      is
          implicitly loaded if it is not already loaded. For more
          information, see
      <a class="xref" href="error-log-configuration.html" title="7.4.2.1 Error Log Configuration">
       Section 7.4.2.1, “Error Log Configuration”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_log_error_suppression_list">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_log_error_suppression_list">
       <code class="literal">
        log_error_suppression_list
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274185920">
     </a>
     <a class="indexterm" name="idm46045274184816">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for log_error_suppression_list">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --log-error-suppression-list=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_log_error_suppression_list">
            log_error_suppression_list
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           empty string
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_log_error_suppression_list">
       <code class="literal">
        log_error_suppression_list
       </code>
      </a>
      system variable applies to events intended for the error log
          and specifies which events to suppress when they occur with a
          priority of
      <code class="literal">
       WARNING
      </code>
      or
      <code class="literal">
       INFORMATION
      </code>
      . For example, if a particular
          type of warning is considered undesirable
      <span class="quote">
       “
       <span class="quote">
        noise
       </span>
       ”
      </span>
      in the error log because it occurs frequently but is not of
          interest, it can be suppressed. This variable affects
          filtering performed by the
      <code class="literal">
       log_filter_internal
      </code>
      error log filter
          component, which is enabled by default (see
      <a class="xref" href="error-log-components.html" title="7.5.3 Error Log Components">
       Section 7.5.3, “Error Log Components”
      </a>
      ). If
      <code class="literal">
       log_filter_internal
      </code>
      is disabled,
      <a class="link" href="server-system-variables.html#sysvar_log_error_suppression_list">
       <code class="literal">
        log_error_suppression_list
       </code>
      </a>
      has no effect.
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_log_error_suppression_list">
       <code class="literal">
        log_error_suppression_list
       </code>
      </a>
      value may be the empty string for no suppression, or a list of
          one or more comma-separated values indicating the error codes
          to suppress. Error codes may be specified in symbolic or
          numeric form. A numeric code may be specified with or without
          the
      <code class="literal">
       MY-
      </code>
      prefix. Leading zeros in the
          numeric part are not significant. Examples of permitted code
          formats:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-simple"><div class="docs-select-all right" id="sa33441907"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">ER_SERVER_SHUTDOWN_COMPLETE
MY<span class="token operator">-</span>000031
000031
MY<span class="token operator">-</span>31
31</code></pre>
     </div>
     <p>
      Symbolic values are preferable to numeric values for
          readability and portability. For information about the
          permitted error symbols and numbers, see
      <a class="ulink" href="/doc/mysql-errors/8.4/en/" target="_top">
       MySQL 8.4 Error Message Reference
      </a>
      .
     </p>
     <p>
      The effect of
      <a class="link" href="server-system-variables.html#sysvar_log_error_suppression_list">
       <code class="literal">
        log_error_suppression_list
       </code>
      </a>
      combines with that of
      <a class="link" href="server-system-variables.html#sysvar_log_error_verbosity">
       <code class="literal">
        log_error_verbosity
       </code>
      </a>
      . For
          additional information, see
      <a class="xref" href="error-log-priority-based-filtering.html" title="7.4.2.5 Priority-Based Error Log Filtering (log_filter_internal)">
       Section 7.4.2.5, “Priority-Based Error Log Filtering (log_filter_internal)”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_log_error_verbosity">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_log_error_verbosity">
       <code class="literal">
        log_error_verbosity
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274143904">
     </a>
     <a class="indexterm" name="idm46045274142864">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for log_error_verbosity">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --log-error-verbosity=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_log_error_verbosity">
            log_error_verbosity
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           2
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           3
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_log_error_verbosity">
       <code class="literal">
        log_error_verbosity
       </code>
      </a>
      system variable specifies the verbosity for handling events
          intended for the error log. This variable affects filtering
          performed by the
      <code class="literal">
       log_filter_internal
      </code>
      error
          log filter component, which is enabled by default (see
      <a class="xref" href="error-log-components.html" title="7.5.3 Error Log Components">
       Section 7.5.3, “Error Log Components”
      </a>
      ). If
      <code class="literal">
       log_filter_internal
      </code>
      is disabled,
      <a class="link" href="server-system-variables.html#sysvar_log_error_verbosity">
       <code class="literal">
        log_error_verbosity
       </code>
      </a>
      has no
          effect.
     </p>
     <p>
      Events intended for the error log have a priority of
      <code class="literal">
       ERROR
      </code>
      ,
      <code class="literal">
       WARNING
      </code>
      , or
      <code class="literal">
       INFORMATION
      </code>
      .
      <a class="link" href="server-system-variables.html#sysvar_log_error_verbosity">
       <code class="literal">
        log_error_verbosity
       </code>
      </a>
      controls
          verbosity based on which priorities to permit for messages
          written to the log, as shown in the following table.
     </p>
     <div class="informaltable">
      <table summary="Permitted log_error_verbosity values and corresponding permitted message priorities">
       <colgroup>
        <col style="width: 40%"/>
        <col style="width: 40%"/>
       </colgroup>
       <thead>
        <tr>
         <th>
          log_error_verbosity Value
         </th>
         <th>
          Permitted Message Priorities
         </th>
        </tr>
       </thead>
       <tbody>
        <tr>
         <td>
          1
         </td>
         <td>
          <code class="literal">
           ERROR
          </code>
         </td>
        </tr>
        <tr>
         <td>
          2
         </td>
         <td>
          <code class="literal">
           ERROR
          </code>
          ,
          <code class="literal">
           WARNING
          </code>
         </td>
        </tr>
        <tr>
         <td>
          3
         </td>
         <td>
          <code class="literal">
           ERROR
          </code>
          ,
          <code class="literal">
           WARNING
          </code>
          ,
          <code class="literal">
           INFORMATION
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      There is also a priority of
      <code class="literal">
       SYSTEM
      </code>
      . System
          messages about non-error situations are printed to the error
          log regardless of the
      <a class="link" href="server-system-variables.html#sysvar_log_error_verbosity">
       <code class="literal">
        log_error_verbosity
       </code>
      </a>
      value.
          These messages include startup and shutdown messages, and some
          significant changes to settings.
     </p>
     <p>
      The effect of
      <a class="link" href="server-system-variables.html#sysvar_log_error_verbosity">
       <code class="literal">
        log_error_verbosity
       </code>
      </a>
      combines
          with that of
      <a class="link" href="server-system-variables.html#sysvar_log_error_suppression_list">
       <code class="literal">
        log_error_suppression_list
       </code>
      </a>
      .
          For additional information, see
      <a class="xref" href="error-log-priority-based-filtering.html" title="7.4.2.5 Priority-Based Error Log Filtering (log_filter_internal)">
       Section 7.4.2.5, “Priority-Based Error Log Filtering (log_filter_internal)”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_log_output">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_log_output">
       <code class="literal">
        log_output
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274083424">
     </a>
     <a class="indexterm" name="idm46045274082336">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for log_output">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --log-output=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_log_output">
            log_output
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Set
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           FILE
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            TABLE
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            FILE
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            NONE
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The destination or destinations for general query log and slow
          query log output. The value is a list one or more
          comma-separated words chosen from
      <code class="literal">
       TABLE
      </code>
      ,
      <code class="literal">
       FILE
      </code>
      , and
      <code class="literal">
       NONE
      </code>
      .
      <code class="literal">
       TABLE
      </code>
      selects logging to the
      <a class="link" href="server-system-variables.html#sysvar_general_log">
       <code class="literal">
        general_log
       </code>
      </a>
      and
      <code class="literal">
       slow_log
      </code>
      tables in the
      <code class="literal">
       mysql
      </code>
      system schema.
      <code class="literal">
       FILE
      </code>
      selects logging to log files.
      <code class="literal">
       NONE
      </code>
      disables logging. If
      <code class="literal">
       NONE
      </code>
      is present in the value, it takes
          precedence over any other words that are present.
      <code class="literal">
       TABLE
      </code>
      and
      <code class="literal">
       FILE
      </code>
      can both
          be given to select both log output destinations.
     </p>
     <p>
      This variable selects log output destinations, but does not
          enable log output. To do that, enable the
      <a class="link" href="server-system-variables.html#sysvar_general_log">
       <code class="literal">
        general_log
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_slow_query_log">
       <code class="literal">
        slow_query_log
       </code>
      </a>
      system
          variables. For
      <code class="literal">
       FILE
      </code>
      logging, the
      <a class="link" href="server-system-variables.html#sysvar_general_log_file">
       <code class="literal">
        general_log_file
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_slow_query_log_file">
       <code class="literal">
        slow_query_log_file
       </code>
      </a>
      system
          variables determine the log file locations. For more
          information, see
      <a class="xref" href="log-destinations.html" title="7.4.1 Selecting General Query Log and Slow Query Log Output Destinations">
       Section 7.4.1, “Selecting General Query Log and Slow Query Log Output Destinations”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_log_queries_not_using_indexes">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_log_queries_not_using_indexes">
       <code class="literal">
        log_queries_not_using_indexes
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274036480">
     </a>
     <a class="indexterm" name="idm46045274035376">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for log_queries_not_using_indexes">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --log-queries-not-using-indexes[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_log_queries_not_using_indexes">
            log_queries_not_using_indexes
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If you enable this variable with the slow query log enabled,
          queries that are expected to retrieve all rows are logged. See
      <a class="xref" href="slow-query-log.html" title="7.4.5 The Slow Query Log">
       Section 7.4.5, “The Slow Query Log”
      </a>
      . This option does not
          necessarily mean that no index is used. For example, a query
          that uses a full index scan uses an index but would be logged
          because the index would not limit the number of rows.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_log_raw">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_log_raw">
       <code class="literal">
        log_raw
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045274009824">
     </a>
     <a class="indexterm" name="idm46045274008752">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for log-raw">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --log-raw[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_log_raw">
            log_raw
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_log_raw">
       <code class="literal">
        log_raw
       </code>
      </a>
      system variable
          is initially set to the value of the
      <a class="link" href="server-options.html#option_mysqld_log-raw">
       <code class="option">
        --log-raw
       </code>
      </a>
      option. See the
          description of that option for more information. The system
          variable may also be set at runtime to change password masking
          behavior.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_log_slow_admin_statements">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_log_slow_admin_statements">
       <code class="literal">
        log_slow_admin_statements
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273981920">
     </a>
     <a class="indexterm" name="idm46045273980400">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for log_slow_admin_statements">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --log-slow-admin-statements[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_log_slow_admin_statements">
            log_slow_admin_statements
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Include slow administrative statements in the statements
          written to the slow query log. Administrative statements
          include
      <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       <code class="literal">
        ALTER TABLE
       </code>
      </a>
      ,
      <a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
       <code class="literal">
        ANALYZE TABLE
       </code>
      </a>
      ,
      <a class="link" href="check-table.html" title="15.7.3.2 CHECK TABLE Statement">
       <code class="literal">
        CHECK TABLE
       </code>
      </a>
      ,
      <a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
       <code class="literal">
        CREATE INDEX
       </code>
      </a>
      ,
      <a class="link" href="drop-index.html" title="15.1.27 DROP INDEX Statement">
       <code class="literal">
        DROP INDEX
       </code>
      </a>
      ,
      <a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
       <code class="literal">
        OPTIMIZE TABLE
       </code>
      </a>
      , and
      <a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
       <code class="literal">
        REPAIR TABLE
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_log_slow_extra">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_log_slow_extra">
       <code class="literal">
        log_slow_extra
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273947184">
     </a>
     <a class="indexterm" name="idm46045273946096">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for log_slow_extra">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --log-slow-extra[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_log_slow_extra">
            log_slow_extra
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If the slow query log is enabled and the output destination
          includes
      <code class="literal">
       FILE
      </code>
      , the server writes additional
          fields to log file lines that provide information about slow
          statements. See
      <a class="xref" href="slow-query-log.html" title="7.4.5 The Slow Query Log">
       Section 7.4.5, “The Slow Query Log”
      </a>
      .
      <code class="literal">
       TABLE
      </code>
      output is unaffected.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_log_timestamps">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_log_timestamps">
       <code class="literal">
        log_timestamps
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273919360">
     </a>
     <a class="indexterm" name="idm46045273918272">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for log_timestamps">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --log-timestamps=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_log_timestamps">
            log_timestamps
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           UTC
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            UTC
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            SYSTEM
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls the time zone of timestamps in messages
          written to the error log, and in general query log and slow
          query log messages written to files. It does not affect the
          time zone of general query log and slow query log messages
          written to tables (
      <code class="literal">
       mysql.general_log
      </code>
      ,
      <code class="literal">
       mysql.slow_log
      </code>
      ). Rows retrieved from those
          tables can be converted from the local system time zone to any
          desired time zone with
      <a class="link" href="date-and-time-functions.html#function_convert-tz">
       <code class="literal">
        CONVERT_TZ()
       </code>
      </a>
      or by setting the
          session
      <a class="link" href="server-system-variables.html#sysvar_time_zone">
       <code class="literal">
        time_zone
       </code>
      </a>
      system
          variable.
     </p>
     <p>
      Permitted
      <a class="link" href="server-system-variables.html#sysvar_log_timestamps">
       <code class="literal">
        log_timestamps
       </code>
      </a>
      values are
      <code class="literal">
       UTC
      </code>
      (the default) and
      <code class="literal">
       SYSTEM
      </code>
      (the local system time zone).
     </p>
     <p>
      Timestamps are written using ISO 8601 / RFC 3339 format:
      <code class="literal">
       <em class="replaceable">
        <code>
         YYYY-MM-DD
        </code>
       </em>
       T
       <em class="replaceable">
        <code>
         hh:mm:ss.uuuuuu
        </code>
       </em>
      </code>
      plus a tail value of
      <code class="literal">
       Z
      </code>
      signifying Zulu time
          (UTC) or
      <code class="literal">
       ±hh:mm
      </code>
      (an offset from
          UTC).
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_log_throttle_queries_not_using_indexes">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_log_throttle_queries_not_using_indexes">
       <code class="literal">
        log_throttle_queries_not_using_indexes
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273878976">
     </a>
     <a class="indexterm" name="idm46045273877936">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for log_throttle_queries_not_using_indexes">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --log-throttle-queries-not-using-indexes=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_log_throttle_queries_not_using_indexes">
            log_throttle_queries_not_using_indexes
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If
      <a class="link" href="server-system-variables.html#sysvar_log_queries_not_using_indexes">
       <code class="literal">
        log_queries_not_using_indexes
       </code>
      </a>
      is enabled, the
      <a class="link" href="server-system-variables.html#sysvar_log_throttle_queries_not_using_indexes">
       <code class="literal">
        log_throttle_queries_not_using_indexes
       </code>
      </a>
      variable limits the number of such queries per minute that can
          be written to the slow query log. A value of 0 (the default)
          means
      <span class="quote">
       “
       <span class="quote">
        no limit
       </span>
       ”
      </span>
      . For more information, see
      <a class="xref" href="slow-query-log.html" title="7.4.5 The Slow Query Log">
       Section 7.4.5, “The Slow Query Log”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_long_query_time">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_long_query_time">
       <code class="literal">
        long_query_time
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273844688">
     </a>
     <a class="indexterm" name="idm46045273843600">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for long_query_time">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --long-query-time=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_long_query_time">
            long_query_time
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Numeric
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           10
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If a query takes longer than this many seconds, the server
          increments the
      <a class="link" href="server-status-variables.html#statvar_Slow_queries">
       <code class="literal">
        Slow_queries
       </code>
      </a>
      status variable. If the slow query log is enabled, the query
          is logged to the slow query log file. This value is measured
          in real time, not CPU time, so a query that is under the
          threshold on a lightly loaded system might be above the
          threshold on a heavily loaded one. The minimum and default
          values of
      <a class="link" href="server-system-variables.html#sysvar_long_query_time">
       <code class="literal">
        long_query_time
       </code>
      </a>
      are 0 and 10, respectively. The maximum is 31536000, which is
          365 days in seconds. The value can be specified to a
          resolution of microseconds. See
      <a class="xref" href="slow-query-log.html" title="7.4.5 The Slow Query Log">
       Section 7.4.5, “The Slow Query Log”
      </a>
      .
     </p>
     <p>
      Smaller values of this variable result in more statements
          being considered long-running, with the result that more space
          is required for the slow query log. For very small values
          (less than one second), the log may grow quite large in a
          small time. Increasing the number of statements considered
          long-running may also result in false positives for the
      <span class="quote">
       “
       <span class="quote">
        excessive Number of Long Running Processes
       </span>
       ”
      </span>
      alert in MySQL Enterprise Monitor, especially if Group Replication is enabled.
          For these reasons, very small values should be used in test
          environments only, or, in production environments, only for a
          short period.
     </p>
     <p>
      <a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
       <span class="command">
        <strong>
         mysqldump
        </strong>
       </span>
      </a>
      performs a full table scan, which
          means its queries can often exceed a
      <a class="link" href="server-system-variables.html#sysvar_long_query_time">
       <code class="literal">
        long_query_time
       </code>
      </a>
      setting that
          is useful for regular queries. If you want to exclude most or
          all of the queries generated by
      <a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
       <span class="command">
        <strong>
         mysqldump
        </strong>
       </span>
      </a>
      from the slow query log, you can use
      <a class="link" href="mysqldump.html#option_mysqldump_mysqld-long-query-time">
       <code class="option">
        --mysqld-long-query-time
       </code>
      </a>
      to
          change the session value of the system variable to a higher
          value.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_low_priority_updates">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_low_priority_updates">
       <code class="literal">
        low_priority_updates
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273801472">
     </a>
     <a class="indexterm" name="idm46045273800432">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for low_priority_updates">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --low-priority-updates[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_low_priority_updates">
            low_priority_updates
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If set to
      <code class="literal">
       1
      </code>
      , all
      <a class="link" href="insert.html" title="15.2.7 INSERT Statement">
       <code class="literal">
        INSERT
       </code>
      </a>
      ,
      <a class="link" href="update.html" title="15.2.17 UPDATE Statement">
       <code class="literal">
        UPDATE
       </code>
      </a>
      ,
      <a class="link" href="delete.html" title="15.2.2 DELETE Statement">
       <code class="literal">
        DELETE
       </code>
      </a>
      , and
      <code class="literal">
       LOCK TABLE
          WRITE
      </code>
      statements wait until there is no pending
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      or
      <code class="literal">
       LOCK TABLE
          READ
      </code>
      on the affected table. The same effect can be
          obtained using
      <code class="literal">
       {INSERT | REPLACE | DELETE | UPDATE}
          LOW_PRIORITY ...
      </code>
      to lower the priority of only one
          query. This variable affects only storage engines that use
          only table-level locking (such as
      <code class="literal">
       MyISAM
      </code>
      ,
      <code class="literal">
       MEMORY
      </code>
      , and
      <code class="literal">
       MERGE
      </code>
      ). See
      <a class="xref" href="table-locking.html" title="10.11.2 Table Locking Issues">
       Section 10.11.2, “Table Locking Issues”
      </a>
      .
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_lower_case_file_system">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_lower_case_file_system">
       <code class="literal">
        lower_case_file_system
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273763536">
     </a>
     <a class="indexterm" name="idm46045273762496">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for lower_case_file_system">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_lower_case_file_system">
            lower_case_file_system
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable describes the case sensitivity of file names on
          the file system where the data directory is located.
      <code class="literal">
       OFF
      </code>
      means file names are case-sensitive,
      <code class="literal">
       ON
      </code>
      means they are not case-sensitive. This
          variable is read only because it reflects a file system
          attribute and setting it would have no effect on the file
          system.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_lower_case_table_names">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_lower_case_table_names">
       <code class="literal">
        lower_case_table_names
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273741088">
     </a>
     <a class="indexterm" name="idm46045273740048">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for lower_case_table_names">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --lower-case-table-names[=#]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_lower_case_table_names">
            lower_case_table_names
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value (macOS)
         </th>
         <td>
          <code class="literal">
           2
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Unix)
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Windows)
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If set to 0, table names are stored as specified and
          comparisons are case-sensitive. If set to 1, table names are
          stored in lowercase on disk and comparisons are not
          case-sensitive. If set to 2, table names are stored as given
          but compared in lowercase. This option also applies to
          database names and table aliases. For additional details, see
      <a class="xref" href="identifier-case-sensitivity.html" title="11.2.3 Identifier Case Sensitivity">
       Section 11.2.3, “Identifier Case Sensitivity”
      </a>
      .
     </p>
     <p>
      The default value of this variable is platform-dependent (see
      <a class="link" href="server-system-variables.html#sysvar_lower_case_file_system">
       <code class="literal">
        lower_case_file_system
       </code>
      </a>
      ). On
          Linux and other Unix-like systems, the default is
      <code class="literal">
       0
      </code>
      . On Windows the default value is
      <code class="literal">
       1
      </code>
      . On macOS, the default value is
      <code class="literal">
       2
      </code>
      . On Linux (and other Unix-like systems),
          setting the value to
      <code class="literal">
       2
      </code>
      is not supported;
          the server forces the value to
      <code class="literal">
       0
      </code>
      instead.
     </p>
     <p>
      You should
      <span class="emphasis">
       <em>
        not
       </em>
      </span>
      set
      <a class="link" href="server-system-variables.html#sysvar_lower_case_table_names">
       <code class="literal">
        lower_case_table_names
       </code>
      </a>
      to 0
          if you are running MySQL on a system where the data directory
          resides on a case-insensitive file system (such as on Windows
          or macOS). It is an unsupported combination that could result
          in a hang condition when running an
      <code class="literal">
       INSERT INTO ...
          SELECT ... FROM
       <em class="replaceable">
        <code>
         tbl_name
        </code>
       </em>
      </code>
      operation with the wrong
      <em class="replaceable">
       <code>
        tbl_name
       </code>
      </em>
      lettercase. With
      <code class="literal">
       MyISAM
      </code>
      , accessing table
          names using different lettercases could cause index
          corruption.
     </p>
     <p>
      An error message is printed and the server exits if you
          attempt to start the server with
      <a class="link" href="server-system-variables.html#sysvar_lower_case_table_names">
       <code class="literal">
        --lower_case_table_names=0
       </code>
      </a>
      on
          a case-insensitive file system.
     </p>
     <p>
      The setting of this variable affects the behavior of
          replication filtering options with regard to case sensitivity.
          For more information, see
      <a class="xref" href="replication-rules.html" title="19.2.5 How Servers Evaluate Replication Filtering Rules">
       Section 19.2.5, “How Servers Evaluate Replication Filtering Rules”
      </a>
      .
     </p>
     <p>
      It is prohibited to start the server with a
      <a class="link" href="server-system-variables.html#sysvar_lower_case_table_names">
       <code class="literal">
        lower_case_table_names
       </code>
      </a>
      setting that is different from the setting used when the
          server was initialized. The restriction is necessary because
          collations used by various data dictionary table fields are
          determined by the setting defined when the server is
          initialized, and restarting the server with a different
          setting would introduce inconsistencies with respect to how
          identifiers are ordered and compared.
     </p>
     <p>
      It is therefore necessary to configure
      <a class="link" href="server-system-variables.html#sysvar_lower_case_table_names">
       <code class="literal">
        lower_case_table_names
       </code>
      </a>
      to the
          desired setting before initializing the server. In most cases,
          this requires configuring
      <a class="link" href="server-system-variables.html#sysvar_lower_case_table_names">
       <code class="literal">
        lower_case_table_names
       </code>
      </a>
      in a
          MySQL option file before starting the MySQL server for the
          first time. For APT installations on Debian and Ubuntu,
          however, the server is initialized for you, and there is no
          opportunity to configure the setting in an option file
          beforehand. You must therefore use the
      <code class="literal">
       debconf-set-selection
      </code>
      utility prior to
          installing MySQL using APT to enable
      <a class="link" href="server-system-variables.html#sysvar_lower_case_table_names">
       <code class="literal">
        lower_case_table_names
       </code>
      </a>
      . To do
          so, run this command before installing MySQL using APT:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa31925790"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">$<span class="token operator">&gt;</span> sudo debconf<span class="token operator">-</span><span class="token keyword">set</span><span class="token operator">-</span>selections <span class="token operator">&lt;&lt;</span><span class="token operator">&lt;</span> <span class="token string">"mysql-server mysql-server/lowercase-table-names select Enabled"</span></code></pre>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_mandatory_roles">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
       <code class="literal">
        mandatory_roles
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273681888">
     </a>
     <a class="indexterm" name="idm46045273680800">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for mandatory_roles">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --mandatory-roles=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
            mandatory_roles
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           empty string
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Roles the server should treat as mandatory. In effect, these
          roles are automatically granted to every user, although
          setting
      <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
       <code class="literal">
        mandatory_roles
       </code>
      </a>
      does
          not actually change any user accounts, and the granted roles
          are not visible in the
      <code class="literal">
       mysql.role_edges
      </code>
      system table.
     </p>
     <p>
      The variable value is a comma-separated list of role names.
          Example:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa47274739"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">PERSIST</span> mandatory_roles <span class="token operator">=</span> <span class="token string">'`role1`@`%`,`role2`,role3,role4@localhost'</span><span class="token punctuation">;</span></code></pre>
     </div>
     <p>
      Setting the runtime value of
      <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
       <code class="literal">
        mandatory_roles
       </code>
      </a>
      requires the
      <a class="link" href="privileges-provided.html#priv_role-admin">
       <code class="literal">
        ROLE_ADMIN
       </code>
      </a>
      privilege, in
          addition to the
      <a class="link" href="privileges-provided.html#priv_system-variables-admin">
       <code class="literal">
        SYSTEM_VARIABLES_ADMIN
       </code>
      </a>
      privilege (or the deprecated
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege) normally
          required to set a global system variable runtime value.
     </p>
     <p>
      Role names consist of a user part and host part in
      <code class="literal">
       <em class="replaceable">
        <code>
         user_name
        </code>
       </em>
       @
       <em class="replaceable">
        <code>
         host_name
        </code>
       </em>
      </code>
      format. The host part, if omitted, defaults to
      <code class="literal">
       %
      </code>
      . For additional information, see
      <a class="xref" href="role-names.html" title="8.2.5 Specifying Role Names">
       Section 8.2.5, “Specifying Role Names”
      </a>
      .
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
       <code class="literal">
        mandatory_roles
       </code>
      </a>
      value is
          a string, so user names and host names, if quoted, must be
          written in a fashion permitted for quoting within quoted
          strings.
     </p>
     <p>
      Roles named in the value of
      <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
       <code class="literal">
        mandatory_roles
       </code>
      </a>
      cannot be
          revoked with
      <a class="link" href="revoke.html" title="15.7.1.8 REVOKE Statement">
       <code class="literal">
        REVOKE
       </code>
      </a>
      or dropped
          with
      <a class="link" href="drop-role.html" title="15.7.1.4 DROP ROLE Statement">
       <code class="literal">
        DROP ROLE
       </code>
      </a>
      or
      <a class="link" href="drop-user.html" title="15.7.1.5 DROP USER Statement">
       <code class="literal">
        DROP USER
       </code>
      </a>
      .
     </p>
     <p>
      To prevent sessions from being made system sessions by
          default, a role that has the
      <a class="link" href="privileges-provided.html#priv_system-user">
       <code class="literal">
        SYSTEM_USER
       </code>
      </a>
      privilege cannot be
          listed in the value of the
      <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
       <code class="literal">
        mandatory_roles
       </code>
      </a>
      system
          variable:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         If
         <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
          <code class="literal">
           mandatory_roles
          </code>
         </a>
         is
              assigned a role at startup that has the
         <a class="link" href="privileges-provided.html#priv_system-user">
          <code class="literal">
           SYSTEM_USER
          </code>
         </a>
         privilege, the
              server writes a message to the error log and exits.
        </p>
       </li>
       <li class="listitem">
        <p>
         If
         <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
          <code class="literal">
           mandatory_roles
          </code>
         </a>
         is
              assigned a role at runtime that has the
         <a class="link" href="privileges-provided.html#priv_system-user">
          <code class="literal">
           SYSTEM_USER
          </code>
         </a>
         privilege, an
              error occurs and the
         <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
          <code class="literal">
           mandatory_roles
          </code>
         </a>
         value
              remains unchanged.
        </p>
       </li>
      </ul>
     </div>
     <p>
      Mandatory roles, like explicitly granted roles, do not take
          effect until activated (see
      <a class="xref" href="roles.html#roles-activating" title="Activating Roles">
       Activating Roles
      </a>
      ). At login time, role
          activation occurs for all granted roles if the
      <a class="link" href="server-system-variables.html#sysvar_activate_all_roles_on_login">
       <code class="literal">
        activate_all_roles_on_login
       </code>
      </a>
      system variable is enabled; otherwise, or for roles that are
          set as default roles otherwise. At runtime,
      <a class="link" href="set-role.html" title="15.7.1.11 SET ROLE Statement">
       <code class="literal">
        SET ROLE
       </code>
      </a>
      activates roles.
     </p>
     <p>
      Roles that do not exist when assigned to
      <a class="link" href="server-system-variables.html#sysvar_mandatory_roles">
       <code class="literal">
        mandatory_roles
       </code>
      </a>
      but are
          created later may require special treatment to be considered
          mandatory. For details, see
      <a class="xref" href="roles.html#mandatory-roles" title="Defining Mandatory Roles">
       Defining Mandatory Roles
      </a>
      .
     </p>
     <p>
      <a class="link" href="show-grants.html" title="15.7.7.22 SHOW GRANTS Statement">
       <code class="literal">
        SHOW GRANTS
       </code>
      </a>
      displays mandatory
          roles according to the rules described in
      <a class="xref" href="show-grants.html" title="15.7.7.22 SHOW GRANTS Statement">
       Section 15.7.7.22, “SHOW GRANTS Statement”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_allowed_packet">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
       <code class="literal">
        max_allowed_packet
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273615568">
     </a>
     <a class="indexterm" name="idm46045273614528">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_allowed_packet">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-allowed-packet=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
            max_allowed_packet
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           67108864
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           1073741824
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum size of one packet or any generated/intermediate
          string, or any parameter sent by the
      <a class="ulink" href="/doc/c-api/8.4/en/mysql-stmt-send-long-data.html" target="_top">
       <code class="literal">
        mysql_stmt_send_long_data()
       </code>
      </a>
      C
          API function. The default is 64MB.
     </p>
     <p>
      The packet message buffer is initialized to
      <a class="link" href="server-system-variables.html#sysvar_net_buffer_length">
       <code class="literal">
        net_buffer_length
       </code>
      </a>
      bytes, but
          can grow up to
      <a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
       <code class="literal">
        max_allowed_packet
       </code>
      </a>
      bytes when
          needed. This value by default is small, to catch large
          (possibly incorrect) packets.
     </p>
     <p>
      You must increase this value if you are using large
      <a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
       <code class="literal">
        BLOB
       </code>
      </a>
      columns or long strings.
          It should be as big as the largest
      <a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
       <code class="literal">
        BLOB
       </code>
      </a>
      you want to use. The
          protocol limit for
      <a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
       <code class="literal">
        max_allowed_packet
       </code>
      </a>
      is 1GB.
          The value should be a multiple of 1024; nonmultiples are
          rounded down to the nearest multiple.
     </p>
     <p>
      When you change the message buffer size by changing the value
          of the
      <a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
       <code class="literal">
        max_allowed_packet
       </code>
      </a>
      variable, you should also change the buffer size on the client
          side if your client program permits it. The default
      <a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
       <code class="literal">
        max_allowed_packet
       </code>
      </a>
      value
          built in to the client library is 1GB, but individual client
          programs might override this. For example,
      <a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
       <span class="command">
        <strong>
         mysql
        </strong>
       </span>
      </a>
      and
      <a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
       <span class="command">
        <strong>
         mysqldump
        </strong>
       </span>
      </a>
      have
          defaults of 16MB and 24MB, respectively. They also enable you
          to change the client-side value by setting
      <a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
       <code class="literal">
        max_allowed_packet
       </code>
      </a>
      on the
          command line or in an option file.
     </p>
     <p>
      The session value of this variable is read only. The client
          can receive up to as many bytes as the session value. However,
          the server does not send to the client more bytes than the
          current global
      <a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
       <code class="literal">
        max_allowed_packet
       </code>
      </a>
      value.
          (The global value could be less than the session value if the
          global value is changed after the client connects.)
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_connect_errors">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_connect_errors">
       <code class="literal">
        max_connect_errors
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273561936">
     </a>
     <a class="indexterm" name="idm46045273560896">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_connect_errors">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-connect-errors=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_connect_errors">
            max_connect_errors
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           100
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      After
      <a class="link" href="server-system-variables.html#sysvar_max_connect_errors">
       <code class="literal">
        max_connect_errors
       </code>
      </a>
      successive connection requests from a host are interrupted
          without a successful connection, the server blocks that host
          from further connections. If a connection from a host is
          established successfully within fewer than
      <a class="link" href="server-system-variables.html#sysvar_max_connect_errors">
       <code class="literal">
        max_connect_errors
       </code>
      </a>
      attempts
          after a previous connection was interrupted, the error count
          for the host is cleared to zero. To unblock blocked hosts,
          flush the host cache; see
      <a class="xref" href="host-cache.html#host-cache-flushing" title="Flushing the Host Cache">
       Flushing the Host Cache
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_connections">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_connections">
       <code class="literal">
        max_connections
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273525440">
     </a>
     <a class="indexterm" name="idm46045273524352">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_connections">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-connections=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_connections">
            max_connections
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           151
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           100000
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum permitted number of simultaneous client
          connections. The maximum effective value is the lesser of the
          effective value of
      <a class="link" href="server-system-variables.html#sysvar_open_files_limit">
       <code class="literal">
        open_files_limit
       </code>
      </a>
      <code class="literal">
       -
          810
      </code>
      , and the value actually set for
      <code class="literal">
       max_connections
      </code>
      .
     </p>
     <p>
      For more information, see
      <a class="xref" href="connection-interfaces.html" title="7.1.12.1 Connection Interfaces">
       Section 7.1.12.1, “Connection Interfaces”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_delayed_threads">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_delayed_threads">
       <code class="literal">
        max_delayed_threads
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273491104">
     </a>
     <a class="indexterm" name="idm46045273490064">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_delayed_threads">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-delayed-threads=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_delayed_threads">
            max_delayed_threads
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           20
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           16384
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This system variable is deprecated (because
      <code class="literal">
       DELAYED
      </code>
      inserts are not supported) and
          subject to removal in a future MySQL release.
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_digest_length">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_digest_length">
       <code class="literal">
        max_digest_length
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273456544">
     </a>
     <a class="indexterm" name="idm46045273455504">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_digest_length">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-digest-length=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_digest_length">
            max_digest_length
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           1048576
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum number of bytes of memory reserved per session for
          computation of normalized statement digests. Once that amount
          of space is used during digest computation, truncation occurs:
          no further tokens from a parsed statement are collected or
          figure into its digest value. Statements that differ only
          after that many bytes of parsed tokens produce the same
          normalized statement digest and are considered identical if
          compared or if aggregated for digest statistics.
     </p>
     <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Warning
      </div>
      <p>
       Setting
       <a class="link" href="server-system-variables.html#sysvar_max_digest_length">
        <code class="literal">
         max_digest_length
        </code>
       </a>
       to zero disables digest production, which also disables
            server functionality that requires digests, such as MySQL Enterprise Firewall.
      </p>
     </div>
     <p>
      Decreasing the
      <a class="link" href="server-system-variables.html#sysvar_max_digest_length">
       <code class="literal">
        max_digest_length
       </code>
      </a>
      value
          reduces memory use but causes the digest value of more
          statements to become indistinguishable if they differ only at
          the end. Increasing the value permits longer statements to be
          distinguished but increases memory use, particularly for
          workloads that involve large numbers of simultaneous sessions
          (the server allocates
      <a class="link" href="server-system-variables.html#sysvar_max_digest_length">
       <code class="literal">
        max_digest_length
       </code>
      </a>
      bytes per
          session).
     </p>
     <p>
      The parser uses this system variable as a limit on the maximum
          length of normalized statement digests that it computes. The
          Performance Schema, if it tracks statement digests, makes a
          copy of the digest value, using the
      <a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_digest_length">
       <code class="literal">
        performance_schema_max_digest_length
       </code>
      </a>
      .
          system variable as a limit on the maximum length of digests
          that it stores. Consequently, if
      <a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_digest_length">
       <code class="literal">
        performance_schema_max_digest_length
       </code>
      </a>
      is less than
      <a class="link" href="server-system-variables.html#sysvar_max_digest_length">
       <code class="literal">
        max_digest_length
       </code>
      </a>
      , digest
          values stored in the Performance Schema are truncated relative
          to the original digest values.
     </p>
     <p>
      For more information about statement digesting, see
      <a class="xref" href="performance-schema-statement-digests.html" title="29.10 Performance Schema Statement Digests and Sampling">
       Section 29.10, “Performance Schema Statement Digests and Sampling”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_error_count">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_error_count">
       <code class="literal">
        max_error_count
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273411408">
     </a>
     <a class="indexterm" name="idm46045273410320">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_error_count">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-error-count=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_error_count">
            max_error_count
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           65535
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum number of error, warning, and information messages
          to be stored for display by the
      <a class="link" href="show-errors.html" title="15.7.7.18 SHOW ERRORS Statement">
       <code class="literal">
        SHOW
          ERRORS
       </code>
      </a>
      and
      <a class="link" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
       <code class="literal">
        SHOW
          WARNINGS
       </code>
      </a>
      statements. This is the same as the number
          of condition areas in the diagnostics area, and thus the
          number of conditions that can be inspected by
      <a class="link" href="get-diagnostics.html" title="15.6.7.3 GET DIAGNOSTICS Statement">
       <code class="literal">
        GET DIAGNOSTICS
       </code>
      </a>
      .
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_execution_time">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_execution_time">
       <code class="literal">
        max_execution_time
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273375536">
     </a>
     <a class="indexterm" name="idm46045273374496">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_execution_time">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-execution-time=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_execution_time">
            max_execution_time
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          milliseconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The execution timeout for
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      statements, in
          milliseconds. If the value is 0, timeouts are not enabled.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_max_execution_time">
       <code class="literal">
        max_execution_time
       </code>
      </a>
      applies as
          follows:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         The global
         <a class="link" href="server-system-variables.html#sysvar_max_execution_time">
          <code class="literal">
           max_execution_time
          </code>
         </a>
         value
              provides the default for the session value for new
              connections. The session value applies to
         <code class="literal">
          SELECT
         </code>
         executions executed within the
              session that include no
         <a class="link" href="optimizer-hints.html#optimizer-hints-execution-time" title="Statement Execution Time Optimizer Hints">
          <code class="literal">
           MAX_EXECUTION_TIME(
           <em class="replaceable">
            <code>
             N
            </code>
           </em>
           )
          </code>
         </a>
         optimizer hint or for which
         <em class="replaceable">
          <code>
           N
          </code>
         </em>
         is 0.
        </p>
       </li>
       <li class="listitem">
        <p>
         <a class="link" href="server-system-variables.html#sysvar_max_execution_time">
          <code class="literal">
           max_execution_time
          </code>
         </a>
         applies to read-only
         <a class="link" href="select.html" title="15.2.13 SELECT Statement">
          <code class="literal">
           SELECT
          </code>
         </a>
         statements. Statements that are not read only are those
              that invoke a stored function that modifies data as a side
              effect.
        </p>
       </li>
       <li class="listitem">
        <p>
         <a class="link" href="server-system-variables.html#sysvar_max_execution_time">
          <code class="literal">
           max_execution_time
          </code>
         </a>
         is
              ignored for
         <a class="link" href="select.html" title="15.2.13 SELECT Statement">
          <code class="literal">
           SELECT
          </code>
         </a>
         statements in stored programs.
        </p>
       </li>
      </ul>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_heap_table_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_heap_table_size">
       <code class="literal">
        max_heap_table_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273327760">
     </a>
     <a class="indexterm" name="idm46045273326720">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_heap_table_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-heap-table-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_heap_table_size">
            max_heap_table_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           16777216
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           16384
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709550592
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294966272
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable sets the maximum size to which user-created
      <code class="literal">
       MEMORY
      </code>
      tables are permitted to grow. The
          value of the variable is used to calculate
      <code class="literal">
       MEMORY
      </code>
      table
      <code class="literal">
       MAX_ROWS
      </code>
      values.
     </p>
     <p>
      Setting this variable has no effect on any existing
      <code class="literal">
       MEMORY
      </code>
      table, unless the table is
          re-created with a statement such as
      <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
       <code class="literal">
        CREATE TABLE
       </code>
      </a>
      or altered with
      <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       <code class="literal">
        ALTER TABLE
       </code>
      </a>
      or
      <a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
       <code class="literal">
        TRUNCATE TABLE
       </code>
      </a>
      . A server
          restart also sets the maximum size of existing
      <code class="literal">
       MEMORY
      </code>
      tables to the global
      <a class="link" href="server-system-variables.html#sysvar_max_heap_table_size">
       <code class="literal">
        max_heap_table_size
       </code>
      </a>
      value.
     </p>
     <p>
      This variable is also used in conjunction with
      <a class="link" href="server-system-variables.html#sysvar_tmp_table_size">
       <code class="literal">
        tmp_table_size
       </code>
      </a>
      to limit the
          size of internal in-memory tables. See
      <a class="xref" href="internal-temporary-tables.html" title="10.4.4 Internal Temporary Table Use in MySQL">
       Section 10.4.4, “Internal Temporary Table Use in MySQL”
      </a>
      .
     </p>
     <p>
      <code class="literal">
       max_heap_table_size
      </code>
      is not replicated. See
      <a class="xref" href="replication-features-memory.html" title="19.5.1.21 Replication and MEMORY Tables">
       Section 19.5.1.21, “Replication and MEMORY Tables”
      </a>
      , and
      <a class="xref" href="replication-features-variables.html" title="19.5.1.39 Replication and Variables">
       Section 19.5.1.39, “Replication and Variables”
      </a>
      , for more
          information.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_insert_delayed_threads">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_insert_delayed_threads">
       <code class="literal">
        max_insert_delayed_threads
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273275072">
     </a>
     <a class="indexterm" name="idm46045273273968">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_insert_delayed_threads">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_insert_delayed_threads">
            max_insert_delayed_threads
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           20
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           16384
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable is a synonym for
      <a class="link" href="server-system-variables.html#sysvar_max_delayed_threads">
       <code class="literal">
        max_delayed_threads
       </code>
      </a>
      . Like
      <a class="link" href="server-system-variables.html#sysvar_max_delayed_threads">
       <code class="literal">
        max_delayed_threads
       </code>
      </a>
      , it is
          deprecated (because
      <code class="literal">
       DELAYED
      </code>
      inserts are not
          supported) and subject to removal in a future MySQL release.
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_join_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_join_size">
       <code class="literal">
        max_join_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273240432">
     </a>
     <a class="indexterm" name="idm46045273239344">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_join_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-join-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_join_size">
            max_join_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This represents a limit on the maximum number of row accesses
          in base tables made by a join. If the server's estimate
          indicates that a greater number of rows than
      <code class="literal">
       max_join_size
      </code>
      must be read from the base
          tables, the statement is rejected with an error.
     </p>
     <p>
      Setting this variable to a value other than
      <code class="literal">
       DEFAULT
      </code>
      resets the value of
      <a class="link" href="server-system-variables.html#sysvar_sql_big_selects">
       <code class="literal">
        sql_big_selects
       </code>
      </a>
      to
      <code class="literal">
       0
      </code>
      . If you set the
      <code class="literal">
       sql_big_selects
      </code>
      value again, the
      <code class="literal">
       max_join_size
      </code>
      variable is ignored.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_length_for_sort_data">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_length_for_sort_data">
       <code class="literal">
        max_length_for_sort_data
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273204368">
     </a>
     <a class="indexterm" name="idm46045273203264">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_length_for_sort_data">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-length-for-sort-data=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_length_for_sort_data">
            max_length_for_sort_data
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           4096
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           4
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           8388608
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable is deprecated, and has no effect in MySQL
          8.4.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_points_in_geometry">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_points_in_geometry">
       <code class="literal">
        max_points_in_geometry
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273169632">
     </a>
     <a class="indexterm" name="idm46045273168592">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_points_in_geometry">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-points-in-geometry=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_points_in_geometry">
            max_points_in_geometry
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           65536
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           3
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           1048576
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum value of the
      <em class="replaceable">
       <code>
        points_per_circle
       </code>
      </em>
      argument to the
      <a class="link" href="spatial-operator-functions.html#function_st-buffer-strategy">
       <code class="literal">
        ST_Buffer_Strategy()
       </code>
      </a>
      function.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_prepared_stmt_count">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_prepared_stmt_count">
       <code class="literal">
        max_prepared_stmt_count
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273137328">
     </a>
     <a class="indexterm" name="idm46045273136288">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_prepared_stmt_count">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-prepared-stmt-count=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_prepared_stmt_count">
            max_prepared_stmt_count
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           16382
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4194304
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable limits the total number of prepared statements
          in the server. It can be used in environments where there is
          the potential for denial-of-service attacks based on running
          the server out of memory by preparing huge numbers of
          statements. If the value is set lower than the current number
          of prepared statements, existing statements are not affected
          and can be used, but no new statements can be prepared until
          the current number drops below the limit. Setting the value to
          0 disables prepared statements.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_seeks_for_key">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_seeks_for_key">
       <code class="literal">
        max_seeks_for_key
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273106240">
     </a>
     <a class="indexterm" name="idm46045273105200">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_seeks_for_key">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-seeks-for-key=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_seeks_for_key">
            max_seeks_for_key
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Windows)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Other, 64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Other, 32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Windows)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Other, 64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Other, 32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Limit the assumed maximum number of seeks when looking up rows
          based on a key. The MySQL optimizer assumes that no more than
          this number of key seeks are required when searching for
          matching rows in a table by scanning an index, regardless of
          the actual cardinality of the index (see
      <a class="xref" href="show-index.html" title="15.7.7.23 SHOW INDEX Statement">
       Section 15.7.7.23, “SHOW INDEX Statement”
      </a>
      ). By setting this to a low value
          (say, 100), you can force MySQL to prefer indexes instead of
          table scans.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_sort_length">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_sort_length">
       <code class="literal">
        max_sort_length
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273064944">
     </a>
     <a class="indexterm" name="idm46045273063856">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_sort_length">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-sort-length=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_sort_length">
            max_sort_length
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           4
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           8388608
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of bytes to use when sorting string values which
          use
      <code class="literal">
       PAD SPACE
      </code>
      collations. The server uses
          only the first
      <a class="link" href="server-system-variables.html#sysvar_max_sort_length">
       <code class="literal">
        max_sort_length
       </code>
      </a>
      bytes of any
          such value and ignores the rest. Consequently, such values
          that differ only after the first
      <a class="link" href="server-system-variables.html#sysvar_max_sort_length">
       <code class="literal">
        max_sort_length
       </code>
      </a>
      bytes compare
          as equal for
      <code class="literal">
       GROUP BY
      </code>
      ,
      <code class="literal">
       ORDER
          BY
      </code>
      , and
      <code class="literal">
       DISTINCT
      </code>
      operations.
          (This behavior differs from previous versions of MySQL, where
          this setting was applied to all values used in comparisons.)
     </p>
     <p>
      Increasing the value of
      <a class="link" href="server-system-variables.html#sysvar_max_sort_length">
       <code class="literal">
        max_sort_length
       </code>
      </a>
      may require
          increasing the value of
      <a class="link" href="server-system-variables.html#sysvar_sort_buffer_size">
       <code class="literal">
        sort_buffer_size
       </code>
      </a>
      as well. For
          details, see
      <a class="xref" href="order-by-optimization.html" title="10.2.1.16 ORDER BY Optimization">
       Section 10.2.1.16, “ORDER BY Optimization”
      </a>
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_sp_recursion_depth">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_sp_recursion_depth">
       <code class="literal">
        max_sp_recursion_depth
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045273022896">
     </a>
     <a class="indexterm" name="idm46045273021856">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_sp_recursion_depth">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-sp-recursion-depth[=#]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_sp_recursion_depth">
            max_sp_recursion_depth
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           255
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of times that any given stored procedure may be
          called recursively. The default value for this option is 0,
          which completely disables recursion in stored procedures. The
          maximum value is 255.
     </p>
     <p>
      Stored procedure recursion increases the demand on thread
          stack space. If you increase the value of
      <a class="link" href="server-system-variables.html#sysvar_max_sp_recursion_depth">
       <code class="literal">
        max_sp_recursion_depth
       </code>
      </a>
      , it
          may be necessary to increase thread stack size by increasing
          the value of
      <a class="link" href="server-system-variables.html#sysvar_thread_stack">
       <code class="literal">
        thread_stack
       </code>
      </a>
      at
          server startup.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_user_connections">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_user_connections">
       <code class="literal">
        max_user_connections
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272989104">
     </a>
     <a class="indexterm" name="idm46045272988064">
     </a>
     <a class="indexterm" name="idm46045272986576">
     </a>
     <a class="indexterm" name="idm46045272985088">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_user_connections">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-user-connections=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_user_connections">
            max_user_connections
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum number of simultaneous connections permitted to
          any given MySQL user account. A value of 0 (the default) means
      <span class="quote">
       “
       <span class="quote">
        no limit.
       </span>
       ”
      </span>
     </p>
     <p>
      This variable has a global value that can be set at server
          startup or runtime. It also has a read-only session value that
          indicates the effective simultaneous-connection limit that
          applies to the account associated with the current session.
          The session value is initialized as follows:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         If the user account has a nonzero
         <code class="literal">
          MAX_USER_CONNECTIONS
         </code>
         resource limit,
              the session
         <a class="link" href="server-system-variables.html#sysvar_max_user_connections">
          <code class="literal">
           max_user_connections
          </code>
         </a>
         value is set to that limit.
        </p>
       </li>
       <li class="listitem">
        <p>
         Otherwise, the session
         <a class="link" href="server-system-variables.html#sysvar_max_user_connections">
          <code class="literal">
           max_user_connections
          </code>
         </a>
         value is set to the global value.
        </p>
       </li>
      </ul>
     </div>
     <p>
      Account resource limits are specified using the
      <a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
       <code class="literal">
        CREATE USER
       </code>
      </a>
      or
      <a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
       <code class="literal">
        ALTER USER
       </code>
      </a>
      statement. See
      <a class="xref" href="user-resources.html" title="8.2.21 Setting Account Resource Limits">
       Section 8.2.21, “Setting Account Resource Limits”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_max_write_lock_count">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_max_write_lock_count">
       <code class="literal">
        max_write_lock_count
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272945120">
     </a>
     <a class="indexterm" name="idm46045272944080">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for max_write_lock_count">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --max-write-lock-count=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_max_write_lock_count">
            max_write_lock_count
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Windows)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Other, 64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Other, 32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Windows)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Other, 64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Other, 32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      After this many write locks, permit some pending read lock
          requests to be processed in between. Write lock requests have
          higher priority than read lock requests. However, if
      <a class="link" href="server-system-variables.html#sysvar_max_write_lock_count">
       <code class="literal">
        max_write_lock_count
       </code>
      </a>
      is set
          to some low value (say, 10), read lock requests may be
          preferred over pending write lock requests if the read lock
          requests have already been passed over in favor of 10 write
          lock requests. Normally this behavior does not occur because
      <a class="link" href="server-system-variables.html#sysvar_max_write_lock_count">
       <code class="literal">
        max_write_lock_count
       </code>
      </a>
      by
          default has a very large value.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_mecab_rc_file">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_mecab_rc_file">
       <code class="literal">
        mecab_rc_file
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272901856">
     </a>
     <a class="indexterm" name="idm46045272900768">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for mecab_rc_file">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --mecab-rc-file=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_mecab_rc_file">
            mecab_rc_file
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <code class="literal">
       mecab_rc_file
      </code>
      option is used when
          setting up the MeCab full-text parser.
     </p>
     <p>
      The
      <code class="literal">
       mecab_rc_file
      </code>
      option defines the path
          to the
      <code class="filename">
       mecabrc
      </code>
      configuration file, which
          is the configuration file for MeCab. The option is read-only
          and can only be set at startup. The
      <code class="filename">
       mecabrc
      </code>
      configuration file is required to
          initialize MeCab.
     </p>
     <p>
      For information about the MeCab full-text parser, see
      <a class="xref" href="fulltext-search-mecab.html" title="14.9.9 MeCab Full-Text Parser Plugin">
       Section 14.9.9, “MeCab Full-Text Parser Plugin”
      </a>
      .
     </p>
     <p>
      For information about options that can be specified in the
          MeCab
      <code class="filename">
       mecabrc
      </code>
      configuration file, refer
          to the
      <a class="ulink" href="http://mecab.googlecode.com/svn/trunk/mecab/doc/index.html" target="_blank">
       MeCab
          Documentation
      </a>
      on the
      <a class="ulink" href="https://code.google.com/" target="_blank">
       Google
          Developers
      </a>
      site.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_min_examined_row_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_min_examined_row_limit">
       <code class="literal">
        min_examined_row_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272871152">
     </a>
     <a class="indexterm" name="idm46045272870112">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for min_examined_row_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --min-examined-row-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_min_examined_row_limit">
            min_examined_row_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Queries that examine fewer than this number of rows are not
          logged to the slow query log.
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_myisam_data_pointer_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_myisam_data_pointer_size">
       <code class="literal">
        myisam_data_pointer_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272836832">
     </a>
     <a class="indexterm" name="idm46045272835728">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for myisam_data_pointer_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --myisam-data-pointer-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_myisam_data_pointer_size">
            myisam_data_pointer_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           6
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           2
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           7
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The default pointer size in bytes, to be used by
      <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
       <code class="literal">
        CREATE TABLE
       </code>
      </a>
      for
      <code class="literal">
       MyISAM
      </code>
      tables when no
      <code class="literal">
       MAX_ROWS
      </code>
      option is specified. This variable
          cannot be less than 2 or larger than 7. The default value is
          6. See
      <a class="xref" href="full-table.html" title="B.3.2.10 The table is full">
       Section B.3.2.10, “The table is full”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_myisam_max_sort_file_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_myisam_max_sort_file_size">
       <code class="literal">
        myisam_max_sort_file_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272800592">
     </a>
     <a class="indexterm" name="idm46045272799488">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for myisam_max_sort_file_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --myisam-max-sort-file-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_myisam_max_sort_file_size">
            myisam_max_sort_file_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Windows)
         </th>
         <td>
          <code class="literal">
           2146435072
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Other, 64-bit platforms)
         </th>
         <td>
          <code class="literal">
           9223372036853727232
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Other, 32-bit platforms)
         </th>
         <td>
          <code class="literal">
           2147483648
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Windows)
         </th>
         <td>
          <code class="literal">
           2146435072
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Other, 64-bit platforms)
         </th>
         <td>
          <code class="literal">
           9223372036853727232
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Other, 32-bit platforms)
         </th>
         <td>
          <code class="literal">
           2147483648
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum size of the temporary file that MySQL is permitted
          to use while re-creating a
      <code class="literal">
       MyISAM
      </code>
      index
          (during
      <a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
       <code class="literal">
        REPAIR TABLE
       </code>
      </a>
      ,
      <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       <code class="literal">
        ALTER TABLE
       </code>
      </a>
      , or
      <a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
       <code class="literal">
        LOAD DATA
       </code>
      </a>
      ). If the file size
          would be larger than this value, the index is created using
          the key cache instead, which is slower. The value is given in
          bytes.
     </p>
     <p>
      If
      <code class="literal">
       MyISAM
      </code>
      index files exceed this size and
          disk space is available, increasing the value may help
          performance. The space must be available in the file system
          containing the directory where the original index file is
          located.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_myisam_mmap_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_myisam_mmap_size">
       <code class="literal">
        myisam_mmap_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272752096">
     </a>
     <a class="indexterm" name="idm46045272751008">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for myisam_mmap_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --myisam-mmap-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_myisam_mmap_size">
            myisam_mmap_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           7
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum amount of memory to use for memory mapping
          compressed
      <a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine">
       <code class="literal">
        MyISAM
       </code>
      </a>
      files. If many
          compressed
      <code class="literal">
       MyISAM
      </code>
      tables are used, the
          value can be decreased to reduce the likelihood of
          memory-swapping problems.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_myisam_recover_options">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_myisam_recover_options">
       <code class="literal">
        myisam_recover_options
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272712512">
     </a>
     <a class="indexterm" name="idm46045272711472">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for myisam_recover_options">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --myisam-recover-options[=list]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_myisam_recover_options">
            myisam_recover_options
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            OFF
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            DEFAULT
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            BACKUP
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            FORCE
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            QUICK
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Set the
      <code class="literal">
       MyISAM
      </code>
      storage engine recovery
          mode. The variable value is any combination of the values of
      <code class="literal">
       OFF
      </code>
      ,
      <code class="literal">
       DEFAULT
      </code>
      ,
      <code class="literal">
       BACKUP
      </code>
      ,
      <code class="literal">
       FORCE
      </code>
      , or
      <code class="literal">
       QUICK
      </code>
      . If you specify multiple values,
          separate them by commas. Specifying the variable with no value
          at server startup is the same as specifying
      <code class="literal">
       DEFAULT
      </code>
      , and specifying with an explicit
          value of
      <code class="literal">
       ""
      </code>
      disables recovery (same as a
          value of
      <code class="literal">
       OFF
      </code>
      ). If recovery is enabled, each
          time
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      opens a
      <code class="literal">
       MyISAM
      </code>
      table, it checks whether the table
          is marked as crashed or was not closed properly. (The last
          option works only if you are running with external locking
          disabled.) If this is the case,
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      runs
          a check on the table. If the table was corrupted,
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      attempts to repair it.
     </p>
     <p>
      The following options affect how the repair works.
     </p>
     <div class="informaltable">
      <table summary="myisam_recover_options system variable values.">
       <colgroup>
        <col style="width: 15%"/>
        <col style="width: 70%"/>
       </colgroup>
       <thead>
        <tr>
         <th>
          Option
         </th>
         <th>
          Description
         </th>
        </tr>
       </thead>
       <tbody>
        <tr>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
         <td>
          No recovery.
         </td>
        </tr>
        <tr>
         <td>
          <code class="literal">
           DEFAULT
          </code>
         </td>
         <td>
          Recovery without backup, forcing, or quick checking.
         </td>
        </tr>
        <tr>
         <td>
          <code class="literal">
           BACKUP
          </code>
         </td>
         <td>
          If the data file was changed during recovery, save a backup of the
          <code class="filename">
           <em class="replaceable">
            <code>
             tbl_name
            </code>
           </em>
           .MYD
          </code>
          file as
          <code class="filename">
           <em class="replaceable">
            <code>
             tbl_name-datetime
            </code>
           </em>
           .BAK
          </code>
          .
         </td>
        </tr>
        <tr>
         <td>
          <code class="literal">
           FORCE
          </code>
         </td>
         <td>
          Run recovery even if we would lose more than one row from the
          <code class="filename">
           .MYD
          </code>
          file.
         </td>
        </tr>
        <tr>
         <td>
          <code class="literal">
           QUICK
          </code>
         </td>
         <td>
          Do not check the rows in the table if there are not any delete blocks.
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Before the server automatically repairs a table, it writes a
          note about the repair to the error log. If you want to be able
          to recover from most problems without user intervention, you
          should use the options
      <code class="literal">
       BACKUP,FORCE
      </code>
      . This
          forces a repair of a table even if some rows would be deleted,
          but it keeps the old data file as a backup so that you can
          later examine what happened.
     </p>
     <p>
      See
      <a class="xref" href="myisam-start.html" title="18.2.1 MyISAM Startup Options">
       Section 18.2.1, “MyISAM Startup Options”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_myisam_sort_buffer_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_myisam_sort_buffer_size">
       <code class="literal">
        myisam_sort_buffer_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272644880">
     </a>
     <a class="indexterm" name="idm46045272643840">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for myisam_sort_buffer_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --myisam-sort-buffer-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_myisam_sort_buffer_size">
            myisam_sort_buffer_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           8388608
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           4096
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The size of the buffer that is allocated when sorting
      <code class="literal">
       MyISAM
      </code>
      indexes during a
      <a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
       <code class="literal">
        REPAIR TABLE
       </code>
      </a>
      or when creating
          indexes with
      <a class="link" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
       <code class="literal">
        CREATE INDEX
       </code>
      </a>
      or
      <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       <code class="literal">
        ALTER TABLE
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_myisam_stats_method">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_myisam_stats_method">
       <code class="literal">
        myisam_stats_method
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272605360">
     </a>
     <a class="indexterm" name="idm46045272604320">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for myisam_stats_method">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --myisam-stats-method=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_myisam_stats_method">
            myisam_stats_method
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           nulls_unequal
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            nulls_unequal
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            nulls_equal
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            nulls_ignored
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      How the server treats
      <code class="literal">
       NULL
      </code>
      values when
          collecting statistics about the distribution of index values
          for
      <code class="literal">
       MyISAM
      </code>
      tables. This variable has three
          possible values,
      <code class="literal">
       nulls_equal
      </code>
      ,
      <code class="literal">
       nulls_unequal
      </code>
      , and
      <code class="literal">
       nulls_ignored
      </code>
      . For
      <code class="literal">
       nulls_equal
      </code>
      , all
      <code class="literal">
       NULL
      </code>
      index values are considered equal and form a single value
          group that has a size equal to the number of
      <code class="literal">
       NULL
      </code>
      values. For
      <code class="literal">
       nulls_unequal
      </code>
      ,
      <code class="literal">
       NULL
      </code>
      values are considered unequal, and each
      <code class="literal">
       NULL
      </code>
      forms a distinct value group of size
          1. For
      <code class="literal">
       nulls_ignored
      </code>
      ,
      <code class="literal">
       NULL
      </code>
      values are ignored.
     </p>
     <p>
      The method that is used for generating table statistics
          influences how the optimizer chooses indexes for query
          execution, as described in
      <a class="xref" href="index-statistics.html" title="10.3.8 InnoDB and MyISAM Index Statistics Collection">
       Section 10.3.8, “InnoDB and MyISAM Index Statistics Collection”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_myisam_use_mmap">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_myisam_use_mmap">
       <code class="literal">
        myisam_use_mmap
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272564208">
     </a>
     <a class="indexterm" name="idm46045272563120">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for myisam_use_mmap">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --myisam-use-mmap[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_myisam_use_mmap">
            myisam_use_mmap
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Use memory mapping for reading and writing
      <code class="literal">
       MyISAM
      </code>
      tables.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_mysql_native_password_proxy_users">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_mysql_native_password_proxy_users">
       <code class="literal">
        mysql_native_password_proxy_users
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272537728">
     </a>
     <a class="indexterm" name="idm46045272536688">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for mysql_native_password_proxy_users">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --mysql-native-password-proxy-users[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_mysql_native_password_proxy_users">
            mysql_native_password_proxy_users
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls whether the
      <a class="link" href="native-pluggable-authentication.html" title="8.4.1.1 Native Pluggable Authentication">
       <code class="literal">
        mysql_native_password
       </code>
      </a>
      built-in authentication plugin (deprecated) supports proxy
          users. It has no effect unless the
      <a class="link" href="server-system-variables.html#sysvar_check_proxy_users">
       <code class="literal">
        check_proxy_users
       </code>
      </a>
      system
          variable and the
      <code class="literal">
       mysql_native_password
      </code>
      plugin are enabled. For information about user proxying, see
      <a class="xref" href="proxy-users.html" title="8.2.19 Proxy Users">
       Section 8.2.19, “Proxy Users”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_named_pipe">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_named_pipe">
       <code class="literal">
        named_pipe
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272505968">
     </a>
     <a class="indexterm" name="idm46045272504880">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for named_pipe">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --named-pipe[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_named_pipe">
            named_pipe
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Platform Specific
         </th>
         <td>
          Windows
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      (Windows only.) Indicates whether the server supports
          connections over named pipes.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_named_pipe_full_access_group">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_named_pipe_full_access_group">
       <code class="literal">
        named_pipe_full_access_group
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272478256">
     </a>
     <a class="indexterm" name="idm46045272477152">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for named_pipe_full_access_group">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --named-pipe-full-access-group=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_named_pipe_full_access_group">
            named_pipe_full_access_group
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Platform Specific
         </th>
         <td>
          Windows
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           empty string
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            empty string
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            valid Windows local group name
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            *everyone*
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      (Windows only.) The access control granted to clients on the
          named pipe created by the MySQL server is set to the minimum
          necessary for successful communication when the
      <a class="link" href="server-system-variables.html#sysvar_named_pipe">
       <code class="literal">
        named_pipe
       </code>
      </a>
      system variable is
          enabled to support named-pipe connections. Some MySQL client
          software can open named pipe connections without any
          additional configuration; however, other client software may
          still require full access to open a named pipe connection.
     </p>
     <p>
      This variable sets the name of a Windows local group whose
          members are granted sufficient access by the MySQL server to
          use named-pipe clients. The default value is an empty string,
          which means that no Windows user is granted full access to the
          named pipe.
     </p>
     <p>
      A new Windows local group name (for example,
      <code class="literal">
       mysql_access_client_users
      </code>
      ) can be created
          in Windows and then used to replace the default value when
          access is absolutely necessary. In this case, limit the
          membership of the group to as few users as possible, removing
          users from the group when their client software is upgraded. A
          non-member of the group who attempts to open a connection to
          MySQL with the affected named-pipe client is denied access
          until a Windows administrator adds the user to the group.
          Newly added users must log out and log in again to join the
          group (required by Windows).
     </p>
     <p>
      Setting the value to
      <code class="literal">
       '*everyone*'
      </code>
      provides
          a language-independent way of referring to the Everyone group
          on Windows. The Everyone group is not secure by default.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_net_buffer_length">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_net_buffer_length">
       <code class="literal">
        net_buffer_length
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272440144">
     </a>
     <a class="indexterm" name="idm46045272439104">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for net_buffer_length">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --net-buffer-length=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_net_buffer_length">
            net_buffer_length
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           16384
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           1048576
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Each client thread is associated with a connection buffer and
          result buffer. Both begin with a size given by
      <a class="link" href="server-system-variables.html#sysvar_net_buffer_length">
       <code class="literal">
        net_buffer_length
       </code>
      </a>
      but are
          dynamically enlarged up to
      <a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
       <code class="literal">
        max_allowed_packet
       </code>
      </a>
      bytes as
          needed. The result buffer shrinks to
      <a class="link" href="server-system-variables.html#sysvar_net_buffer_length">
       <code class="literal">
        net_buffer_length
       </code>
      </a>
      after each
          SQL statement.
     </p>
     <p>
      This variable should not normally be changed, but if you have
          very little memory, you can set it to the expected length of
          statements sent by clients. If statements exceed this length,
          the connection buffer is automatically enlarged. The maximum
          value to which
      <a class="link" href="server-system-variables.html#sysvar_net_buffer_length">
       <code class="literal">
        net_buffer_length
       </code>
      </a>
      can be set
          is 1MB.
     </p>
     <p>
      The session value of this variable is read only.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_net_read_timeout">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_net_read_timeout">
       <code class="literal">
        net_read_timeout
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272398192">
     </a>
     <a class="indexterm" name="idm46045272397104">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for net_read_timeout">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --net-read-timeout=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_net_read_timeout">
            net_read_timeout
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           30
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of seconds to wait for more data from a connection
          before aborting the read. When the server is reading from the
          client,
      <a class="link" href="server-system-variables.html#sysvar_net_read_timeout">
       <code class="literal">
        net_read_timeout
       </code>
      </a>
      is
          the timeout value controlling when to abort. When the server
          is writing to the client,
      <a class="link" href="server-system-variables.html#sysvar_net_write_timeout">
       <code class="literal">
        net_write_timeout
       </code>
      </a>
      is the
          timeout value controlling when to abort. See also
      <a class="link" href="replication-options-replica.html#sysvar_replica_net_timeout">
       <code class="literal">
        replica_net_timeout
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_net_retry_count">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_net_retry_count">
       <code class="literal">
        net_retry_count
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272361712">
     </a>
     <a class="indexterm" name="idm46045272360624">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for net_retry_count">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --net-retry-count=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_net_retry_count">
            net_retry_count
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           10
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If a read or write on a communication port is interrupted,
          retry this many times before giving up. This value should be
          set quite high on FreeBSD because internal interrupts are sent
          to all threads.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_net_write_timeout">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_net_write_timeout">
       <code class="literal">
        net_write_timeout
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272328528">
     </a>
     <a class="indexterm" name="idm46045272327488">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for net_write_timeout">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --net-write-timeout=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_net_write_timeout">
            net_write_timeout
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           60
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of seconds to wait for a block to be written to a
          connection before aborting the write. See also
      <a class="link" href="server-system-variables.html#sysvar_net_read_timeout">
       <code class="literal">
        net_read_timeout
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ngram_token_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ngram_token_size">
       <code class="literal">
        ngram_token_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272294784">
     </a>
     <a class="indexterm" name="idm46045272293696">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ngram_token_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ngram-token-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ngram_token_size">
            ngram_token_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           2
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           10
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Defines the n-gram token size for the n-gram full-text parser.
          The
      <code class="literal">
       ngram_token_size
      </code>
      option is read-only
          and can only be modified at startup. The default value is 2
          (bigram). The maximum value is 10.
     </p>
     <p>
      For more information about how to configure this variable, see
      <a class="xref" href="fulltext-search-ngram.html" title="14.9.8 ngram Full-Text Parser">
       Section 14.9.8, “ngram Full-Text Parser”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_offline_mode">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_offline_mode">
       <code class="literal">
        offline_mode
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272262256">
     </a>
     <a class="indexterm" name="idm46045272261168">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for offline_mode">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --offline-mode[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_offline_mode">
            offline_mode
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      In offline mode, the MySQL instance disconnects client users
          unless they have relevant privileges, and does not allow them
          to initiate new connections. Clients that are refused access
          receive an
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_server_offline_mode" target="_top">
       <code class="literal">
        ER_SERVER_OFFLINE_MODE
       </code>
      </a>
      error.
     </p>
     <p>
      To put a server in offline mode, change the value of the
      <a class="link" href="server-system-variables.html#sysvar_offline_mode">
       <code class="literal">
        offline_mode
       </code>
      </a>
      system variable
          from
      <code class="literal">
       OFF
      </code>
      to
      <code class="literal">
       ON
      </code>
      . To
          resume normal operations, change
      <a class="link" href="server-system-variables.html#sysvar_offline_mode">
       <code class="literal">
        offline_mode
       </code>
      </a>
      from
      <code class="literal">
       ON
      </code>
      to
      <code class="literal">
       OFF
      </code>
      . To control
          offline mode, an administrator account must have the
      <a class="link" href="privileges-provided.html#priv_system-variables-admin">
       <code class="literal">
        SYSTEM_VARIABLES_ADMIN
       </code>
      </a>
      privilege and the
      <a class="link" href="privileges-provided.html#priv_connection-admin">
       <code class="literal">
        CONNECTION_ADMIN
       </code>
      </a>
      privilege (or
          the deprecated
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege,
          which covers both these privileges).
      <a class="link" href="privileges-provided.html#priv_connection-admin">
       <code class="literal">
        CONNECTION_ADMIN
       </code>
      </a>
      is required,
          to prevent accidental lockout.
     </p>
     <p>
      Offline mode has these characteristics:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         Connected client users who do not have the
         <a class="link" href="privileges-provided.html#priv_connection-admin">
          <code class="literal">
           CONNECTION_ADMIN
          </code>
         </a>
         privilege
              (or the deprecated
         <a class="link" href="privileges-provided.html#priv_super">
          <code class="literal">
           SUPER
          </code>
         </a>
         privilege) are disconnected on the next request, with an
              appropriate error. Disconnection includes terminating
              running statements and releasing locks. Such clients also
              cannot initiate new connections, and receive an
              appropriate error.
        </p>
       </li>
       <li class="listitem">
        <p>
         Connected client users who have the
         <a class="link" href="privileges-provided.html#priv_connection-admin">
          <code class="literal">
           CONNECTION_ADMIN
          </code>
         </a>
         or
         <a class="link" href="privileges-provided.html#priv_super">
          <code class="literal">
           SUPER
          </code>
         </a>
         privilege are not
              disconnected, and can initiate new connections to manage
              the server.
        </p>
       </li>
       <li class="listitem">
        <p>
         If the user that puts a server in offline mode does not
              have the
         <a class="link" href="privileges-provided.html#priv_system-user">
          <code class="literal">
           SYSTEM_USER
          </code>
         </a>
         privilege, connected client users who have the
         <a class="link" href="privileges-provided.html#priv_system-user">
          <code class="literal">
           SYSTEM_USER
          </code>
         </a>
         privilege are
              also not disconnected. However, these users cannot
              initiate new connections to the server while it is in
              offline mode, unless they have the
         <a class="link" href="privileges-provided.html#priv_connection-admin">
          <code class="literal">
           CONNECTION_ADMIN
          </code>
         </a>
         or
         <a class="link" href="privileges-provided.html#priv_super">
          <code class="literal">
           SUPER
          </code>
         </a>
         privilege as well. It
              is only their existing connection that cannot be
              terminated, because the
         <a class="link" href="privileges-provided.html#priv_system-user">
          <code class="literal">
           SYSTEM_USER
          </code>
         </a>
         privilege is
              required to kill a session or statement that is executing
              with the
         <a class="link" href="privileges-provided.html#priv_system-user">
          <code class="literal">
           SYSTEM_USER
          </code>
         </a>
         privilege.
        </p>
       </li>
       <li class="listitem">
        <p>
         Replication threads are permitted to keep applying data to
              the server.
        </p>
       </li>
      </ul>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_old_alter_table">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_old_alter_table">
       <code class="literal">
        old_alter_table
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272206800">
     </a>
     <a class="indexterm" name="idm46045272205712">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for old_alter_table">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --old-alter-table[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_old_alter_table">
            old_alter_table
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      When this variable is enabled, the server does not use the
          optimized method of processing an
      <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       <code class="literal">
        ALTER
          TABLE
       </code>
      </a>
      operation. It reverts to using a temporary
          table, copying over the data, and then renaming the temporary
          table to the original, as used by MySQL 5.0 and earlier. For
          more information on the operation of
      <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       <code class="literal">
        ALTER TABLE
       </code>
      </a>
      , see
      <a class="xref" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       Section 15.1.9, “ALTER TABLE Statement”
      </a>
      .
     </p>
     <p>
      <code class="literal">
       ALTER TABLE ... DROP PARTITION
      </code>
      with
      <a class="link" href="server-system-variables.html#sysvar_old_alter_table">
       <code class="literal">
        old_alter_table=ON
       </code>
      </a>
      rebuilds
          the partitioned table and attempts to move data from the
          dropped partition to another partition with a compatible
      <code class="literal">
       PARTITION ... VALUES
      </code>
      definition. Data that
          cannot be moved to another partition is deleted. In earlier
          releases,
      <code class="literal">
       ALTER TABLE ... DROP PARTITION
      </code>
      with
      <a class="link" href="server-system-variables.html#sysvar_old_alter_table">
       <code class="literal">
        old_alter_table=ON
       </code>
      </a>
      deletes data stored in the partition and drops the partition.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_open_files_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_open_files_limit">
       <code class="literal">
        open_files_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272172560">
     </a>
     <a class="indexterm" name="idm46045272171472">
     </a>
     <a class="indexterm" name="idm46045272169984">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for open_files_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --open-files-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_open_files_limit">
            open_files_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           5000, with possible adjustment
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           platform dependent
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of file descriptors available to
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      from the operating system:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         At startup,
         <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
          <span class="command">
           <strong>
            mysqld
           </strong>
          </span>
         </a>
         reserves descriptors
              with
         <code class="function">
          setrlimit()
         </code>
         , using the value
              requested at by setting this variable directly or by using
              the
         <a class="link" href="mysqld-safe.html#option_mysqld_safe_open-files-limit">
          <code class="option">
           --open-files-limit
          </code>
         </a>
         option to
         <a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
          <span class="command">
           <strong>
            mysqld_safe
           </strong>
          </span>
         </a>
         . If
         <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
          <span class="command">
           <strong>
            mysqld
           </strong>
          </span>
         </a>
         produces the error
         <code class="literal">
          Too
              many open files
         </code>
         , try increasing the
         <a class="link" href="server-system-variables.html#sysvar_open_files_limit">
          <code class="literal">
           open_files_limit
          </code>
         </a>
         value.
              Internally, the maximum value for this variable is the
              maximum unsigned integer value, but the actual maximum is
              platform dependent.
        </p>
       </li>
       <li class="listitem">
        <p>
         At runtime, the value of
         <a class="link" href="server-system-variables.html#sysvar_open_files_limit">
          <code class="literal">
           open_files_limit
          </code>
         </a>
         indicates the number of file descriptors actually
              permitted to
         <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
          <span class="command">
           <strong>
            mysqld
           </strong>
          </span>
         </a>
         by the operating
              system, which might differ from the value requested at
              startup. If the number of file descriptors requested
              during startup cannot be allocated,
         <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
          <span class="command">
           <strong>
            mysqld
           </strong>
          </span>
         </a>
         writes a warning to the error
              log.
        </p>
       </li>
      </ul>
     </div>
     <p>
      The effective
      <a class="link" href="server-system-variables.html#sysvar_open_files_limit">
       <code class="literal">
        open_files_limit
       </code>
      </a>
      value is
          based on the value specified at system startup (if any) and
          the values of
      <a class="link" href="server-system-variables.html#sysvar_max_connections">
       <code class="literal">
        max_connections
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_table_open_cache">
       <code class="literal">
        table_open_cache
       </code>
      </a>
      , using
          these formulas:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          10 + max_connections + (table_open_cache *
              2)
         </code>
         . Using the defaults for these variables
              yields 8161.
        </p>
        <p>
         On Windows only, 2048 (the value of the C Run-Time Library
              file descriptor maximum) is added to this number. This
              totals 10209, again using the default values for the
              indicated system variables.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          max_connections * 5
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         The operating system limit.
        </p>
       </li>
      </ul>
     </div>
     <p>
      The server attempts to obtain the number of file descriptors
          using the maximum of those values, capped to the maximum
          unsigned integer value. If that many descriptors cannot be
          obtained, the server attempts to obtain as many as the system
          permits.
     </p>
     <p>
      The effective value is 0 on systems where MySQL cannot change
          the number of open files.
     </p>
     <p>
      On Unix, the value cannot be set greater than the value
          displayed by the
      <span class="command">
       <strong>
        ulimit -n
       </strong>
      </span>
      command. On
          Linux systems using
      <code class="literal">
       systemd
      </code>
      , the value
          cannot be set greater than
      <code class="literal">
       LimitNOFILE
      </code>
      (this is
      <code class="literal">
       DefaultLimitNOFILE
      </code>
      , if
      <code class="literal">
       LimitNOFILE
      </code>
      is not set); otherwise, on
          Linux, the value of
      <code class="literal">
       open_files_limit
      </code>
      cannot
          exceed
      <span class="command">
       <strong>
        ulimit -n
       </strong>
      </span>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_optimizer_prune_level">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_optimizer_prune_level">
       <code class="literal">
        optimizer_prune_level
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272109408">
     </a>
     <a class="indexterm" name="idm46045272108368">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for optimizer_prune_level">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --optimizer-prune-level=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_optimizer_prune_level">
            optimizer_prune_level
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Controls the heuristics applied during query optimization to
          prune less-promising partial plans from the optimizer search
          space. A value of 0 disables heuristics so that the optimizer
          performs an exhaustive search. A value of 1 causes the
          optimizer to prune plans based on the number of rows retrieved
          by intermediate plans.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_optimizer_search_depth">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_optimizer_search_depth">
       <code class="literal">
        optimizer_search_depth
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272078592">
     </a>
     <a class="indexterm" name="idm46045272077552">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for optimizer_search_depth">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --optimizer-search-depth=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_optimizer_search_depth">
            optimizer_search_depth
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           62
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           62
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum depth of search performed by the query optimizer.
          Values larger than the number of relations in a query result
          in better query plans, but take longer to generate an
          execution plan for a query. Values smaller than the number of
          relations in a query return an execution plan quicker, but the
          resulting plan may be far from being optimal. If set to 0, the
          system automatically picks a reasonable value.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_optimizer_switch">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_optimizer_switch">
       <code class="literal">
        optimizer_switch
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045272047856">
     </a>
     <a class="indexterm" name="idm46045272046768">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for optimizer_switch">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --optimizer-switch=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_optimizer_switch">
            optimizer_switch
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Set
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            batched_key_access={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            block_nested_loop={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            condition_fanout_filter={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            derived_condition_pushdown={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            derived_merge={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            duplicateweedout={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            engine_condition_pushdown={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            firstmatch={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            hash_join={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            index_condition_pushdown={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            index_merge={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            index_merge_intersection={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            index_merge_sort_union={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            index_merge_union={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            loosescan={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            materialization={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            mrr={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            mrr_cost_based={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            prefer_ordering_index={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            semijoin={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            skip_scan={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            subquery_materialization_cost_based={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            subquery_to_derived={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            use_index_extensions={on|off}
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            use_invisible_indexes={on|off}
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_optimizer_switch">
       <code class="literal">
        optimizer_switch
       </code>
      </a>
      system
          variable enables control over optimizer behavior. The value of
          this variable is a set of flags, each of which has a value of
      <code class="literal">
       on
      </code>
      or
      <code class="literal">
       off
      </code>
      to indicate
          whether the corresponding optimizer behavior is enabled or
          disabled. This variable has global and session values and can
          be changed at runtime. The global default can be set at server
          startup.
     </p>
     <p>
      To see the current set of optimizer flags, select the variable
          value:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa3805627"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql&gt;</span> <span class="token keyword">SELECT</span> <span class="token variable">@@optimizer_switch</span>\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
@@optimizer_switch<span class="token punctuation">:</span> index_merge=on,index_merge_union=on,
                    index_merge_sort_union=on,index_merge_intersection=on,
                    engine_condition_pushdown=on,index_condition_pushdown=on,
                    mrr=on,mrr_cost_based=on,block_nested_loop=on,
                    batched_key_access=off,materialization=on,semijoin=on,
                    loosescan=on,firstmatch=on,duplicateweedout=on,
                    subquery_materialization_cost_based=on,
                    use_index_extensions=on,condition_fanout_filter=on,
                    derived_merge=on,use_invisible_indexes=off,skip_scan=on,
                    hash_join=on,subquery_to_derived=off,
                    prefer_ordering_index=on,hypergraph_optimizer=off,
                    derived_condition_pushdown=on,hash_set_operations=on
</span><span class="token output">1 row in set (0.00 sec)</span></code></pre>
     </div>
     <p>
      For more information about the syntax of this variable and the
          optimizer behaviors that it controls, see
      <a class="xref" href="switchable-optimizations.html" title="10.9.2 Switchable Optimizations">
       Section 10.9.2, “Switchable Optimizations”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_optimizer_trace">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_optimizer_trace">
       <code class="literal">
        optimizer_trace
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271991776">
     </a>
     <a class="indexterm" name="idm46045271990688">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for optimizer_trace">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --optimizer-trace=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_optimizer_trace">
            optimizer_trace
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls optimizer tracing. For details, see
      <a class="xref" href="optimizer-tracing.html" title="10.15 Tracing the Optimizer">
       Section 10.15, “Tracing the Optimizer”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_optimizer_trace_features">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_optimizer_trace_features">
       <code class="literal">
        optimizer_trace_features
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271967888">
     </a>
     <a class="indexterm" name="idm46045271966784">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for optimizer_trace_features">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --optimizer-trace-features=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_optimizer_trace_features">
            optimizer_trace_features
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable enables or disables selected optimizer tracing
          features. For details, see
      <a class="xref" href="optimizer-tracing.html" title="10.15 Tracing the Optimizer">
       Section 10.15, “Tracing the Optimizer”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_optimizer_trace_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_optimizer_trace_limit">
       <code class="literal">
        optimizer_trace_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271943840">
     </a>
     <a class="indexterm" name="idm46045271942800">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for optimizer_trace_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --optimizer-trace-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_optimizer_trace_limit">
            optimizer_trace_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2147483647
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum number of optimizer traces to display. For
          details, see
      <a class="xref" href="optimizer-tracing.html" title="10.15 Tracing the Optimizer">
       Section 10.15, “Tracing the Optimizer”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_optimizer_trace_max_mem_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_optimizer_trace_max_mem_size">
       <code class="literal">
        optimizer_trace_max_mem_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271912656">
     </a>
     <a class="indexterm" name="idm46045271911552">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for optimizer_trace_max_mem_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --optimizer-trace-max-mem-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_optimizer_trace_max_mem_size">
            optimizer_trace_max_mem_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1048576
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum cumulative size of stored optimizer traces. For
          details, see
      <a class="xref" href="optimizer-tracing.html" title="10.15 Tracing the Optimizer">
       Section 10.15, “Tracing the Optimizer”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_optimizer_trace_offset">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_optimizer_trace_offset">
       <code class="literal">
        optimizer_trace_offset
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271879248">
     </a>
     <a class="indexterm" name="idm46045271878208">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for optimizer_trace_offset">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --optimizer-trace-offset=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_optimizer_trace_offset">
            optimizer_trace_offset
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           -1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           -2147483647
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2147483647
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The offset of optimizer traces to display. For details, see
      <a class="xref" href="optimizer-tracing.html" title="10.15 Tracing the Optimizer">
       Section 10.15, “Tracing the Optimizer”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       performance_schema_
       <em class="replaceable">
        <code>
         xxx
        </code>
       </em>
      </code>
     </p>
     <p>
      Performance Schema system variables are listed in
      <a class="xref" href="performance-schema-system-variables.html" title="29.15 Performance Schema System Variables">
       Section 29.15, “Performance Schema System Variables”
      </a>
      . These
          variables may be used to configure Performance Schema
          operation.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_parser_max_mem_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_parser_max_mem_size">
       <code class="literal">
        parser_max_mem_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271845008">
     </a>
     <a class="indexterm" name="idm46045271843968">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for parser_max_mem_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --parser-max-mem-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_parser_max_mem_size">
            parser_max_mem_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           10000000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum amount of memory available to the parser. The
          default value places no limit on memory available. The value
          can be reduced to protect against out-of-memory situations
          caused by parsing long or complex SQL statements.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_partial_revokes">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
       <code class="literal">
        partial_revokes
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271807408">
     </a>
     <a class="indexterm" name="idm46045271806320">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for partial_revokes">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --partial-revokes[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
            partial_revokes
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            OFF
           </code>
           (if partial revokes do not exist)
          </p>
          <p class="valid-value">
           <code class="literal">
            ON
           </code>
           (if partial revokes exist)
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Enabling this variable makes it possible to revoke privileges
          partially. Specifically, for users who have privileges at the
          global level,
      <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
       <code class="literal">
        partial_revokes
       </code>
      </a>
      enables privileges for specific schemas to be revoked while
          leaving the privileges in place for other schemas. For
          example, a user who has the global
      <a class="link" href="privileges-provided.html#priv_update">
       <code class="literal">
        UPDATE
       </code>
      </a>
      privilege can be
          restricted from exercising this privilege on the
      <code class="literal">
       mysql
      </code>
      system schema. (Or, stated another
          way, the user is enabled to exercise the
      <a class="link" href="privileges-provided.html#priv_update">
       <code class="literal">
        UPDATE
       </code>
      </a>
      privilege on all schemas
          except the
      <code class="literal">
       mysql
      </code>
      schema.) In this sense,
          the user's global
      <a class="link" href="privileges-provided.html#priv_update">
       <code class="literal">
        UPDATE
       </code>
      </a>
      privilege is partially revoked.
     </p>
     <p>
      Once enabled,
      <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
       <code class="literal">
        partial_revokes
       </code>
      </a>
      cannot be disabled if any account has privilege restrictions.
          If any such account exists, disabling
      <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
       <code class="literal">
        partial_revokes
       </code>
      </a>
      fails:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         For attempts to disable
         <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
          <code class="literal">
           partial_revokes
          </code>
         </a>
         at
              startup, the server logs an error message and enables
         <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
          <code class="literal">
           partial_revokes
          </code>
         </a>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         For attempts to disable
         <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
          <code class="literal">
           partial_revokes
          </code>
         </a>
         at
              runtime, an error occurs and the
         <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
          <code class="literal">
           partial_revokes
          </code>
         </a>
         value
              remains unchanged.
        </p>
       </li>
      </ul>
     </div>
     <p>
      To disable
      <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
       <code class="literal">
        partial_revokes
       </code>
      </a>
      in
          this case, first modify each account that has partially
          revoked privileges, either by re-granting the privileges or by
          removing the account.
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       In privilege assignments, enabling
       <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
        <code class="literal">
         partial_revokes
        </code>
       </a>
       causes
            MySQL to interpret occurrences of unescaped
       <code class="literal">
        _
       </code>
       and
       <code class="literal">
        %
       </code>
       SQL wildcard
            characters in schema names as literal characters, just as if
            they had been escaped as
       <code class="literal">
        \_
       </code>
       and
       <code class="literal">
        \%
       </code>
       . Because this changes how MySQL
            interprets privileges, it may be advisable to avoid
            unescaped wildcard characters in privilege assignments for
            installations where
       <a class="link" href="server-system-variables.html#sysvar_partial_revokes">
        <code class="literal">
         partial_revokes
        </code>
       </a>
       may be
            enabled.
      </p>
      <p>
       In addition, use of
       <code class="literal">
        _
       </code>
       and
       <code class="literal">
        %
       </code>
       as wildcard characters in grants is
            deprecated, and you should expect support for them to be
            removed in a future version of MySQL.
      </p>
     </div>
     <p>
      For more information, including instructions for removing
          partial revokes, see
      <a class="xref" href="partial-revokes.html" title="8.2.12 Privilege Restriction Using Partial Revokes">
       Section 8.2.12, “Privilege Restriction Using Partial Revokes”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_password_history">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_password_history">
       <code class="literal">
        password_history
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271751488">
     </a>
     <a class="indexterm" name="idm46045271750400">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for password_history">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --password-history=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_password_history">
            password_history
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable defines the global policy for controlling reuse
          of previous passwords based on required minimum number of
          password changes. For an account password used previously,
          this variable indicates the number of subsequent account
          password changes that must occur before the password can be
          reused. If the value is 0 (the default), there is no reuse
          restriction based on number of password changes.
     </p>
     <p>
      Changes to this variable apply immediately to all accounts
          defined with the
      <code class="literal">
       PASSWORD HISTORY DEFAULT
      </code>
      option.
     </p>
     <p>
      The global number-of-changes password reuse policy can be
          overridden as desired for individual accounts using the
      <code class="literal">
       PASSWORD HISTORY
      </code>
      option of the
      <a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
       <code class="literal">
        CREATE USER
       </code>
      </a>
      and
      <a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
       <code class="literal">
        ALTER USER
       </code>
      </a>
      statements. See
      <a class="xref" href="password-management.html" title="8.2.15 Password Management">
       Section 8.2.15, “Password Management”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_password_require_current">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_password_require_current">
       <code class="literal">
        password_require_current
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271714976">
     </a>
     <a class="indexterm" name="idm46045271713872">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for password_require_current">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --password-require-current[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_password_require_current">
            password_require_current
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable defines the global policy for controlling
          whether attempts to change an account password must specify
          the current password to be replaced.
     </p>
     <p>
      Changes to this variable apply immediately to all accounts
          defined with the
      <code class="literal">
       PASSWORD REQUIRE CURRENT
          DEFAULT
      </code>
      option.
     </p>
     <p>
      The global verification-required policy can be overridden as
          desired for individual accounts using the
      <code class="literal">
       PASSWORD
          REQUIRE
      </code>
      option of the
      <a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
       <code class="literal">
        CREATE
          USER
       </code>
      </a>
      and
      <a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
       <code class="literal">
        ALTER USER
       </code>
      </a>
      statements. See
      <a class="xref" href="password-management.html" title="8.2.15 Password Management">
       Section 8.2.15, “Password Management”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_password_reuse_interval">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_password_reuse_interval">
       <code class="literal">
        password_reuse_interval
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271683504">
     </a>
     <a class="indexterm" name="idm46045271682464">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for password_reuse_interval">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --password-reuse-interval=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_password_reuse_interval">
            password_reuse_interval
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          days
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable defines the global policy for controlling reuse
          of previous passwords based on time elapsed. For an account
          password used previously, this variable indicates the number
          of days that must pass before the password can be reused. If
          the value is 0 (the default), there is no reuse restriction
          based on time elapsed.
     </p>
     <p>
      Changes to this variable apply immediately to all accounts
          defined with the
      <code class="literal">
       PASSWORD REUSE INTERVAL
          DEFAULT
      </code>
      option.
     </p>
     <p>
      The global time-elapsed password reuse policy can be
          overridden as desired for individual accounts using the
      <code class="literal">
       PASSWORD REUSE INTERVAL
      </code>
      option of the
      <a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
       <code class="literal">
        CREATE USER
       </code>
      </a>
      and
      <a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
       <code class="literal">
        ALTER USER
       </code>
      </a>
      statements. See
      <a class="xref" href="password-management.html" title="8.2.15 Password Management">
       Section 8.2.15, “Password Management”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_persisted_globals_load">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_persisted_globals_load">
       <code class="literal">
        persisted_globals_load
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271644928">
     </a>
     <a class="indexterm" name="idm46045271643888">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for persisted_globals_load">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --persisted-globals-load[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_persisted_globals_load">
            persisted_globals_load
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether to load persisted configuration settings from the
      <code class="filename">
       mysqld-auto.cnf
      </code>
      file in the data
          directory. The server normally processes this file at startup
          after all other option files (see
      <a class="xref" href="option-files.html" title="6.2.2.2 Using Option Files">
       Section 6.2.2.2, “Using Option Files”
      </a>
      ). Disabling
      <a class="link" href="server-system-variables.html#sysvar_persisted_globals_load">
       <code class="literal">
        persisted_globals_load
       </code>
      </a>
      causes
          the server startup sequence to skip
      <code class="literal">
       mysqld-auto.cnf
      </code>
      .
     </p>
     <a class="indexterm" name="idm46045271618176">
     </a>
     <a class="indexterm" name="idm46045271617136">
     </a>
     <p>
      To modify the contents of
      <code class="filename">
       mysqld-auto.cnf
      </code>
      , use the
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
          PERSIST
       </code>
      </a>
      ,
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
          PERSIST_ONLY
       </code>
      </a>
      , and
      <a class="link" href="reset-persist.html" title="15.7.8.7 RESET PERSIST Statement">
       <code class="literal">
        RESET
          PERSIST
       </code>
      </a>
      statements. See
      <a class="xref" href="persisted-system-variables.html" title="7.1.9.3 Persisted System Variables">
       Section 7.1.9.3, “Persisted System Variables”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_persist_only_admin_x509_subject">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_persist_only_admin_x509_subject">
       <code class="literal">
        persist_only_admin_x509_subject
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271607392">
     </a>
     <a class="indexterm" name="idm46045271606288">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for persist_only_admin_x509_subject">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --persist-only-admin-x509-subject=string
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_persist_only_admin_x509_subject">
            persist_only_admin_x509_subject
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           empty string
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
          PERSIST
       </code>
      </a>
      and
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
          PERSIST_ONLY
       </code>
      </a>
      enable system variables to be persisted
          to the
      <code class="filename">
       mysqld-auto.cnf
      </code>
      option file in the
          data directory (see
      <a class="xref" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       Section 15.7.6.1, “SET Syntax for Variable Assignment”
      </a>
      ).
          Persisting system variables enables runtime configuration
          changes that affect subsequent server restarts, which is
          convenient for remote administration not requiring direct
          access to MySQL server host option files. However, some system
          variables are nonpersistible or can be persisted only under
          certain restrictive conditions.
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_persist_only_admin_x509_subject">
       <code class="literal">
        persist_only_admin_x509_subject
       </code>
      </a>
      system variable specifies the SSL certificate X.509 Subject
          value that users must have to be able to persist system
          variables that are persist-restricted. The default value is
          the empty string, which disables the Subject check so that
          persist-restricted system variables cannot be persisted by any
          user.
     </p>
     <p>
      If
      <a class="link" href="server-system-variables.html#sysvar_persist_only_admin_x509_subject">
       <code class="literal">
        persist_only_admin_x509_subject
       </code>
      </a>
      is nonempty, users who connect to the server using an
          encrypted connection and supply an SSL certificate with the
          designated Subject value then can use
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
          PERSIST_ONLY
       </code>
      </a>
      to persist persist-restricted system
          variables. For information about persist-restricted system
          variables and instructions for configuring MySQL to enable
      <a class="link" href="server-system-variables.html#sysvar_persist_only_admin_x509_subject">
       <code class="literal">
        persist_only_admin_x509_subject
       </code>
      </a>
      ,
          see
      <a class="xref" href="nonpersistible-system-variables.html" title="7.1.9.4 Nonpersistible and Persist-Restricted System Variables">
       Section 7.1.9.4, “Nonpersistible and Persist-Restricted System Variables”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_persist_sensitive_variables_in_plaintext">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_persist_sensitive_variables_in_plaintext">
       <code class="literal">
        persist_sensitive_variables_in_plaintext
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271569744">
     </a>
     <a class="indexterm" name="idm46045271568624">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for persist_sensitive_variables_in_plaintext">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --persist_sensitive_variables_in_plaintext[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_persist_sensitive_variables_in_plaintext">
            persist_sensitive_variables_in_plaintext
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      <code class="literal">
       persist_sensitive_variables_in_plaintext
      </code>
      controls whether the server is permitted to store the values
          of sensitive system variables in an unencrypted format, if
          keyring component support is not available at the time when
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
          PERSIST
       </code>
      </a>
      is used to set the value of the system
          variable. It also controls whether or not the server can start
          if the encrypted values cannot be decrypted. Note that keyring
          plugins do not support secure storage of sensitive system
          variables; a keyring component (see
      <a class="xref" href="keyring.html" title="8.4.4 The MySQL Keyring">
       Section 8.4.4, “The MySQL Keyring”
      </a>
      )
          must be enabled on the MySQL Server instance to support secure
          storage.
     </p>
     <p>
      The default setting,
      <code class="literal">
       ON
      </code>
      , encrypts the
          values if keyring component support is available, and persists
          them unencrypted (with a warning) if it is not. The next time
          any persisted system variable is set, if keyring support is
          available at that time, the server encrypts the values of any
          unencrypted sensitive system variables. The
      <code class="literal">
       ON
      </code>
      setting also allows the server to start
          if encrypted system variable values cannot be decrypted, in
          which case a warning is issued and the default values for the
          system variables are used. In that situation, their values
          cannot be changed until they can be decrypted.
     </p>
     <p>
      The most secure setting,
      <code class="literal">
       OFF
      </code>
      , means
          sensitive system variable values cannot be persisted if
          keyring component support is unavailable. The
      <code class="literal">
       OFF
      </code>
      setting also means the server does not
          start if encrypted system variable values cannot be decrypted.
     </p>
     <p>
      For more information, see
      <a class="xref" href="persisted-system-variables.html#persisted-system-variables-sensitive" title="Persisting Sensitive System Variables">
       Persisting Sensitive System Variables
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_pid_file">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_pid_file">
       <code class="literal">
        pid_file
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271534528">
     </a>
     <a class="indexterm" name="idm46045271533440">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for pid_file">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --pid-file=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_pid_file">
            pid_file
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The path name of the file in which the server writes its
          process ID. The server creates the file in the data directory
          unless an absolute path name is given to specify a different
          directory. If you specify this variable, you must specify a
          value. If you do not specify this variable, MySQL uses a
          default value of
      <code class="filename">
       <em class="replaceable">
        <code>
         host_name
        </code>
       </em>
       .pid
      </code>
      ,
          where
      <em class="replaceable">
       <code>
        host_name
       </code>
      </em>
      is the name of the
          host machine.
     </p>
     <p>
      The process ID file is used by other programs such as
      <a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
       <span class="command">
        <strong>
         mysqld_safe
        </strong>
       </span>
      </a>
      to determine the server's
          process ID. On Windows, this variable also affects the default
          error log file name. See
      <a class="xref" href="error-log.html" title="7.4.2 The Error Log">
       Section 7.4.2, “The Error Log”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_plugin_dir">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_plugin_dir">
       <code class="literal">
        plugin_dir
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271507184">
     </a>
     <a class="indexterm" name="idm46045271506096">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for plugin_dir">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --plugin-dir=dir_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_plugin_dir">
            plugin_dir
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Directory name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           BASEDIR/lib/plugin
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The path name of the plugin directory.
     </p>
     <p>
      If the plugin directory is writable by the server, it may be
          possible for a user to write executable code to a file in the
          directory using
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
          ... INTO DUMPFILE
       </code>
      </a>
      . This can be prevented by making
      <a class="link" href="server-system-variables.html#sysvar_plugin_dir">
       <code class="literal">
        plugin_dir
       </code>
      </a>
      read only to the
          server or by setting
      <a class="link" href="server-system-variables.html#sysvar_secure_file_priv">
       <code class="literal">
        secure_file_priv
       </code>
      </a>
      to a
          directory where
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      writes
          can be made safely.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_port">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_port">
       <code class="literal">
        port
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271475968">
     </a>
     <a class="indexterm" name="idm46045271474896">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for port">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --port=port_num
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_port">
            port
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           3306
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           65535
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of the port on which the server listens for TCP/IP
          connections. This variable can be set with the
      <a class="link" href="server-options.html#option_mysqld_port">
       <code class="option">
        --port
       </code>
      </a>
      option.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_preload_buffer_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_preload_buffer_size">
       <code class="literal">
        preload_buffer_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271444416">
     </a>
     <a class="indexterm" name="idm46045271443376">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for preload_buffer_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --preload-buffer-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_preload_buffer_size">
            preload_buffer_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           32768
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           1073741824
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The size of the buffer that is allocated when preloading
          indexes.
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_print_identified_with_as_hex">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_print_identified_with_as_hex">
       <code class="literal">
        print_identified_with_as_hex
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271410496">
     </a>
     <a class="indexterm" name="idm46045271409392">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for print_identified_with_as_hex">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --print-identified-with-as-hex[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_print_identified_with_as_hex">
            print_identified_with_as_hex
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Password hash values displayed in the
      <code class="literal">
       IDENTIFIED
          WITH
      </code>
      clause of output from
      <a class="link" href="show-create-user.html" title="15.7.7.13 SHOW CREATE USER Statement">
       <code class="literal">
        SHOW
          CREATE USER
       </code>
      </a>
      may contain unprintable characters that
          have adverse effects on terminal displays and in other
          environments. Enabling
      <a class="link" href="server-system-variables.html#sysvar_print_identified_with_as_hex">
       <code class="literal">
        print_identified_with_as_hex
       </code>
      </a>
      causes
      <a class="link" href="show-create-user.html" title="15.7.7.13 SHOW CREATE USER Statement">
       <code class="literal">
        SHOW CREATE USER
       </code>
      </a>
      to
          display such hash values as hexadecimal strings rather than as
          regular string literals. Hash values that do not contain
          unprintable characters still display as regular string
          literals, even with this variable enabled.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_profiling">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_profiling">
       <code class="literal">
        profiling
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271379856">
     </a>
     <a class="indexterm" name="idm46045271378768">
     </a>
     <p>
      If set to 0 or
      <code class="literal">
       OFF
      </code>
      (the default), statement
          profiling is disabled. If set to 1 or
      <code class="literal">
       ON
      </code>
      ,
          statement profiling is enabled and the
      <a class="link" href="show-profile.html" title="15.7.7.32 SHOW PROFILE Statement">
       <code class="literal">
        SHOW PROFILE
       </code>
      </a>
      and
      <a class="link" href="show-profiles.html" title="15.7.7.33 SHOW PROFILES Statement">
       <code class="literal">
        SHOW PROFILES
       </code>
      </a>
      statements
          provide access to profiling information. See
      <a class="xref" href="show-profiles.html" title="15.7.7.33 SHOW PROFILES Statement">
       Section 15.7.7.33, “SHOW PROFILES Statement”
      </a>
      .
     </p>
     <p>
      This variable is deprecated; expect it to be removed in a
          future MySQL release.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_profiling_history_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_profiling_history_size">
       <code class="literal">
        profiling_history_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271369136">
     </a>
     <a class="indexterm" name="idm46045271368096">
     </a>
     <p>
      The number of statements for which to maintain profiling
          information if
      <a class="link" href="server-system-variables.html#sysvar_profiling">
       <code class="literal">
        profiling
       </code>
      </a>
      is
          enabled. The default value is 15. The maximum value is 100.
          Setting the value to 0 effectively disables profiling. See
      <a class="xref" href="show-profiles.html" title="15.7.7.33 SHOW PROFILES Statement">
       Section 15.7.7.33, “SHOW PROFILES Statement”
      </a>
      .
     </p>
     <p>
      This variable is deprecated; expect it to be removed in a
          future MySQL release.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_protocol_compression_algorithms">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_protocol_compression_algorithms">
       <code class="literal">
        protocol_compression_algorithms
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271361072">
     </a>
     <a class="indexterm" name="idm46045271359968">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for protocol_compression_algorithms">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --protocol-compression-algorithms=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_protocol_compression_algorithms">
            protocol_compression_algorithms
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Set
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           zlib,zstd,uncompressed
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            zlib
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            zstd
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            uncompressed
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The compression algorithms that the server permits for
          incoming connections. These include connections by client
          programs and by servers participating in source/replica
          replication or Group Replication. Compression does not apply
          to connections for
      <code class="literal">
       FEDERATED
      </code>
      tables.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_protocol_compression_algorithms">
       <code class="literal">
        protocol_compression_algorithms
       </code>
      </a>
      does not control connection compression for X Protocol. See
      <a class="xref" href="x-plugin-connection-compression.html" title="22.5.5 Connection Compression with X Plugin">
       Section 22.5.5, “Connection Compression with X Plugin”
      </a>
      for
          information on how this operates.
     </p>
     <p>
      The variable value is a list of one or more comma-separated
          compression algorithm names, in any order, chosen from the
          following items (not case-sensitive):
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          zlib
         </code>
         : Permit connections that use the
         <code class="literal">
          zlib
         </code>
         compression algorithm.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          zstd
         </code>
         : Permit connections that use the
         <code class="literal">
          zstd
         </code>
         compression algorithm.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          uncompressed
         </code>
         : Permit uncompressed
              connections. If this algorithm name is not included in the
         <a class="link" href="server-system-variables.html#sysvar_protocol_compression_algorithms">
          <code class="literal">
           protocol_compression_algorithms
          </code>
         </a>
         value, the server does not permit uncompressed
              connections. It permits only compressed connections that
              use whichever other algorithms are specified in the value,
              and there is no fallback to uncompressed connections.
        </p>
       </li>
      </ul>
     </div>
     <p>
      The default value of
      <code class="literal">
       zlib,zstd,uncompressed
      </code>
      indicates that the server permits all compression algorithms.
     </p>
     <p>
      For more information, see
      <a class="xref" href="connection-compression-control.html" title="6.2.8 Connection Compression Control">
       Section 6.2.8, “Connection Compression Control”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_protocol_version">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_protocol_version">
       <code class="literal">
        protocol_version
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271316224">
     </a>
     <a class="indexterm" name="idm46045271315136">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for protocol_version">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_protocol_version">
            protocol_version
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           10
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The version of the client/server protocol used by the MySQL
          server.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_proxy_user">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_proxy_user">
       <code class="literal">
        proxy_user
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271288240">
     </a>
     <a class="indexterm" name="idm46045271287152">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for proxy_user">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_proxy_user">
            proxy_user
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If the current client is a proxy for another user, this
          variable is the proxy user account name. Otherwise, this
          variable is
      <code class="literal">
       NULL
      </code>
      . See
      <a class="xref" href="proxy-users.html" title="8.2.19 Proxy Users">
       Section 8.2.19, “Proxy Users”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_pseudo_replica_mode">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_pseudo_replica_mode">
       <code class="literal">
        pseudo_replica_mode
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271266032">
     </a>
     <a class="indexterm" name="idm46045271264992">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for pseudo_replica_mode">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_pseudo_replica_mode">
            pseudo_replica_mode
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_pseudo_replica_mode">
       <code class="literal">
        pseudo_replica_mode
       </code>
      </a>
      is for
          internal server use. It assists with the correct handling of
          transactions that originated on older or newer servers than
          the server currently processing them.
      <a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
       <span class="command">
        <strong>
         mysqlbinlog
        </strong>
       </span>
      </a>
      sets the value of
      <a class="link" href="server-system-variables.html#sysvar_pseudo_replica_mode">
       <code class="literal">
        pseudo_replica_mode
       </code>
      </a>
      to true
          before executing any SQL statements.
     </p>
     <p>
      Setting the session value of
      <a class="link" href="server-system-variables.html#sysvar_pseudo_replica_mode">
       <code class="literal">
        pseudo_replica_mode
       </code>
      </a>
      is a
          restricted operation. The session user must have either the
      <a class="link" href="privileges-provided.html#priv_replication-applier">
       <code class="literal">
        REPLICATION_APPLIER
       </code>
      </a>
      privilege
          (see
      <a class="xref" href="replication-privilege-checks.html" title="19.3.3 Replication Privilege Checks">
       Section 19.3.3, “Replication Privilege Checks”
      </a>
      ), or
          privileges sufficient to set restricted session variables (see
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      ). However, note
          that the variable is not intended for users to set; it is set
          automatically by the replication infrastructure.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_pseudo_replica_mode">
       <code class="literal">
        pseudo_replica_mode
       </code>
      </a>
      has the
          following effects on the handling of prepared XA transactions,
          which can be attached to or detached from the handling session
          (by default, the session that issues
      <a class="link" href="xa.html" title="15.3.8 XA Transactions">
       <code class="literal">
        XA START
       </code>
      </a>
      ):
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         If true, and the handling session has executed an
              internal-use
         <a class="link" href="binlog.html" title="15.7.8.1 BINLOG Statement">
          <code class="literal">
           BINLOG
          </code>
         </a>
         statement, XA transactions are automatically detached from
              the session as soon as the first part of the transaction
              up to
         <a class="link" href="xa.html" title="15.3.8 XA Transactions">
          <code class="literal">
           XA
              PREPARE
          </code>
         </a>
         finishes, so they can be committed or
              rolled back by any session that has the
         <a class="link" href="privileges-provided.html#priv_xa-recover-admin">
          <code class="literal">
           XA_RECOVER_ADMIN
          </code>
         </a>
         privilege.
        </p>
       </li>
       <li class="listitem">
        <p>
         If false, XA transactions remain attached to the handling
              session as long as that session is alive, during which
              time no other session can commit the transaction. The
              prepared transaction is only detached if the session
              disconnects or the server restarts.
        </p>
       </li>
      </ul>
     </div>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_pseudo_replica_mode">
       <code class="literal">
        pseudo_replica_mode
       </code>
      </a>
      has the
          following effects on the
      <code class="literal">
       original_commit_timestamp
      </code>
      replication delay
          timestamp and the
      <a class="link" href="replication-options-source.html#sysvar_original_server_version">
       <code class="literal">
        original_server_version
       </code>
      </a>
      system variable:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         If true, transactions that do not explicitly set
         <code class="literal">
          original_commit_timestamp
         </code>
         or
         <a class="link" href="replication-options-source.html#sysvar_original_server_version">
          <code class="literal">
           original_server_version
          </code>
         </a>
         are assumed to originate on another, unknown server, so
              the value 0, meaning unknown, is assigned to both the
              timestamp and the system variable.
        </p>
       </li>
       <li class="listitem">
        <p>
         If false, transactions that do not explicitly set
         <code class="literal">
          original_commit_timestamp
         </code>
         or
         <a class="link" href="replication-options-source.html#sysvar_original_server_version">
          <code class="literal">
           original_server_version
          </code>
         </a>
         are assumed to originate on the current server, so the
              current timestamp and the current server's version are
              assigned to the timestamp and the system variable.
        </p>
       </li>
      </ul>
     </div>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_pseudo_replica_mode">
       <code class="literal">
        pseudo_replica_mode
       </code>
      </a>
      has the
          following effects on the handling of a statement that sets one
          or more unsupported (removed or unknown) SQL modes:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         If true, the server ignores the unsupported mode and
              raises a warning.
        </p>
       </li>
       <li class="listitem">
        <p>
         If false, the server rejects the statement with
         <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_unsupported_sql_mode" target="_top">
          <code class="literal">
           ER_UNSUPPORTED_SQL_MODE
          </code>
         </a>
         .
        </p>
       </li>
      </ul>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_pseudo_slave_mode">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_pseudo_slave_mode">
       <code class="literal">
        pseudo_slave_mode
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271211472">
     </a>
     <a class="indexterm" name="idm46045271210432">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for pseudo_slave_mode">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_pseudo_slave_mode">
            pseudo_slave_mode
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Deprecated alias for
      <a class="link" href="server-system-variables.html#sysvar_pseudo_replica_mode">
       <code class="literal">
        pseudo_replica_mode
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_pseudo_thread_id">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_pseudo_thread_id">
       <code class="literal">
        pseudo_thread_id
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271187616">
     </a>
     <a class="indexterm" name="idm46045271186528">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for pseudo_thread_id">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_pseudo_thread_id">
            pseudo_thread_id
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           2147483647
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2147483647
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable is for internal server use.
     </p>
     <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Warning
      </div>
      <p>
       Changing the session value of the
       <a class="link" href="server-system-variables.html#sysvar_pseudo_thread_id">
        <code class="literal">
         pseudo_thread_id
        </code>
       </a>
       system
            variable changes the value returned by the
       <a class="link" href="information-functions.html#function_connection-id">
        <code class="literal">
         CONNECTION_ID()
        </code>
       </a>
       function.
      </p>
     </div>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_query_alloc_block_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_query_alloc_block_size">
       <code class="literal">
        query_alloc_block_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271154832">
     </a>
     <a class="indexterm" name="idm46045271153792">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for query_alloc_block_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --query-alloc-block-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_query_alloc_block_size">
            query_alloc_block_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           8192
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294966272
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The allocation size in bytes of memory blocks that are
          allocated for objects created during statement parsing and
          execution. If you have problems with memory fragmentation, it
          might help to increase this parameter.
     </p>
     <p>
      The block size for the byte number is 1024. A value that is
          not an exact multiple of the block size is rounded down to the
          next lower multiple of the block size by MySQL Server before
          storing the value for the system variable. The parser allows
          values up to the maximum unsigned integer value for the
          platform (4294967295 or 2
      <sup>
       32
      </sup>
      −1
          for a 32-bit system, 18446744073709551615 or
          2
      <sup>
       64
      </sup>
      −1 for a 64-bit system)
          but the actual maximum is a block size lower.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_query_prealloc_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_query_prealloc_size">
       <code class="literal">
        query_prealloc_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271117328">
     </a>
     <a class="indexterm" name="idm46045271116288">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for query_prealloc_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --query-prealloc-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_query_prealloc_size">
            query_prealloc_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           8192
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           8192
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709550592
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294966272
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      <code class="literal">
       query_prealloc_size
      </code>
      is deprecated, and
          setting it has no effect; you should expect its removal in a
          future release of MySQL.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_rand_seed1">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_rand_seed1">
       <code class="literal">
        rand_seed1
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271075856">
     </a>
     <a class="indexterm" name="idm46045271074768">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for rand_seed1">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_rand_seed1">
            rand_seed1
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           N/A
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_rand_seed1">
       <code class="literal">
        rand_seed1
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_rand_seed2">
       <code class="literal">
        rand_seed2
       </code>
      </a>
      variables exist as
          session variables only, and can be set but not read. The
          variables—but not their values—are shown in the
          output of
      <a class="link" href="show-variables.html" title="15.7.7.41 SHOW VARIABLES Statement">
       <code class="literal">
        SHOW VARIABLES
       </code>
      </a>
      .
     </p>
     <p>
      The purpose of these variables is to support replication of
          the
      <a class="link" href="mathematical-functions.html#function_rand">
       <code class="literal">
        RAND()
       </code>
      </a>
      function. For
          statements that invoke
      <a class="link" href="mathematical-functions.html#function_rand">
       <code class="literal">
        RAND()
       </code>
      </a>
      ,
          the source passes two values to the replica, where they are
          used to seed the random number generator. The replica uses
          these values to set the session variables
      <a class="link" href="server-system-variables.html#sysvar_rand_seed1">
       <code class="literal">
        rand_seed1
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_rand_seed2">
       <code class="literal">
        rand_seed2
       </code>
      </a>
      so that
      <a class="link" href="mathematical-functions.html#function_rand">
       <code class="literal">
        RAND()
       </code>
      </a>
      on the replica generates
          the same value as on the source.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_rand_seed2">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_rand_seed2">
       <code class="literal">
        rand_seed2
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271036848">
     </a>
     <a class="indexterm" name="idm46045271035760">
     </a>
     <p>
      See the description for
      <a class="link" href="server-system-variables.html#sysvar_rand_seed1">
       <code class="literal">
        rand_seed1
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_range_alloc_block_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_range_alloc_block_size">
       <code class="literal">
        range_alloc_block_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045271030080">
     </a>
     <a class="indexterm" name="idm46045271029040">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for range_alloc_block_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --range-alloc-block-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_range_alloc_block_size">
            range_alloc_block_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           4096
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           4096
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709550592
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294966272
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The size in bytes of blocks that are allocated when doing
          range optimization.
     </p>
     <p>
      The block size for the byte number is 1024. A value that is
          not an exact multiple of the block size is rounded down to the
          next lower multiple of the block size by MySQL Server before
          storing the value for the system variable. The parser allows
          values up to the maximum unsigned integer value for the
          platform (4294967295 or 2
      <sup>
       32
      </sup>
      −1
          for a 32-bit system, 18446744073709551615 or
          2
      <sup>
       64
      </sup>
      −1 for a 64-bit system)
          but the actual maximum is a block size lower.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_range_optimizer_max_mem_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_range_optimizer_max_mem_size">
       <code class="literal">
        range_optimizer_max_mem_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270990240">
     </a>
     <a class="indexterm" name="idm46045270989136">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for range_optimizer_max_mem_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --range-optimizer-max-mem-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_range_optimizer_max_mem_size">
            range_optimizer_max_mem_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           8388608
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The limit on memory consumption for the range optimizer. A
          value of 0 means
      <span class="quote">
       “
       <span class="quote">
        no limit.
       </span>
       ”
      </span>
      If an execution plan
          considered by the optimizer uses the range access method but
          the optimizer estimates that the amount of memory needed for
          this method would exceed the limit, it abandons the plan and
          considers other plans. For more information, see
      <a class="xref" href="range-optimization.html#range-optimization-memory-use" title="Limiting Memory Use for Range Optimization">
       Limiting Memory Use for Range Optimization
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_rbr_exec_mode">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_rbr_exec_mode">
       <code class="literal">
        rbr_exec_mode
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270956240">
     </a>
     <a class="indexterm" name="idm46045270955152">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for rbr_exec_mode">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_rbr_exec_mode">
            rbr_exec_mode
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           STRICT
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            STRICT
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            IDEMPOTENT
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      For internal use by
      <a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
       <span class="command">
        <strong>
         mysqlbinlog
        </strong>
       </span>
      </a>
      . This
          variable switches the server between
      <code class="literal">
       IDEMPOTENT
      </code>
      mode and
      <code class="literal">
       STRICT
      </code>
      mode.
      <code class="literal">
       IDEMPOTENT
      </code>
      mode causes suppression of duplicate-key and no-key-found
          errors in
      <a class="link" href="binlog.html" title="15.7.8.1 BINLOG Statement">
       <code class="literal">
        BINLOG
       </code>
      </a>
      statements
          generated by
      <a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
       <span class="command">
        <strong>
         mysqlbinlog
        </strong>
       </span>
      </a>
      . This mode is
          useful when replaying a row-based binary log on a server that
          causes conflicts with existing data.
      <a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
       <span class="command">
        <strong>
         mysqlbinlog
        </strong>
       </span>
      </a>
      sets this mode when you specify
          the
      <a class="link" href="mysqlbinlog.html#option_mysqlbinlog_idempotent">
       <code class="option">
        --idempotent
       </code>
      </a>
      option by
          writing the following to the output:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa39869036"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">SESSION</span> RBR_EXEC_MODE<span class="token operator">=</span>IDEMPOTENT<span class="token punctuation">;</span></code></pre>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_read_buffer_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_read_buffer_size">
       <code class="literal">
        read_buffer_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270920032">
     </a>
     <a class="indexterm" name="idm46045270918944">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for read_buffer_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --read-buffer-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_read_buffer_size">
            read_buffer_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           131072
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           8192
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2147479552
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           4096
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Each thread that does a sequential scan for a
      <code class="literal">
       MyISAM
      </code>
      table allocates a buffer of this
          size (in bytes) for each table it scans. If you do many
          sequential scans, you might want to increase this value, which
          defaults to 131072. The value of this variable should be a
          multiple of 4KB. If it is set to a value that is not a
          multiple of 4KB, its value is rounded down to the nearest
          multiple of 4KB.
     </p>
     <p>
      This option is also used in the following context for all
          other storage engines with the exception of
      <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
       <code class="literal">
        InnoDB
       </code>
      </a>
      :
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         For caching the indexes in a temporary file (not a
              temporary table), when sorting rows for
         <code class="literal">
          ORDER
              BY
         </code>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         For bulk insert into partitions.
        </p>
       </li>
       <li class="listitem">
        <p>
         For caching results of nested queries.
        </p>
       </li>
      </ul>
     </div>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_read_buffer_size">
       <code class="literal">
        read_buffer_size
       </code>
      </a>
      is also used
          in one other storage engine-specific way: to determine the
          memory block size for
      <a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
       <code class="literal">
        MEMORY
       </code>
      </a>
      tables.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_select_into_buffer_size">
       <code class="literal">
        select_into_buffer_size
       </code>
      </a>
      is
          used for the I/O cache buffer for
      <a class="link" href="select-into.html" title="15.2.13.1 SELECT ... INTO Statement">
       <code class="literal">
        SELECT INTO
          DUMPFILE
       </code>
      </a>
      and
      <code class="literal">
       SELECT INTO OUTFILE
      </code>
      statements. (
      <a class="link" href="server-system-variables.html#sysvar_read_buffer_size">
       <code class="literal">
        read_buffer_size
       </code>
      </a>
      is used for the I/O cache buffer size in all other cases.)
     </p>
     <p>
      For more information about memory use during different
          operations, see
      <a class="xref" href="memory-use.html" title="10.12.3.1 How MySQL Uses Memory">
       Section 10.12.3.1, “How MySQL Uses Memory”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_read_only">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_read_only">
       <code class="literal">
        read_only
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270868656">
     </a>
     <a class="indexterm" name="idm46045270867568">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for read_only">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --read-only[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_read_only">
            read_only
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If the
      <a class="link" href="server-system-variables.html#sysvar_read_only">
       <code class="literal">
        read_only
       </code>
      </a>
      system
          variable is enabled, the server permits no client updates
          except from users who have the
      <a class="link" href="privileges-provided.html#priv_connection-admin">
       <code class="literal">
        CONNECTION_ADMIN
       </code>
      </a>
      privilege (or
          the deprecated
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege). This variable is disabled by default.
     </p>
     <p>
      The server also supports a
      <a class="link" href="server-system-variables.html#sysvar_super_read_only">
       <code class="literal">
        super_read_only
       </code>
      </a>
      system
          variable (disabled by default), which has these effects:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         If
         <a class="link" href="server-system-variables.html#sysvar_super_read_only">
          <code class="literal">
           super_read_only
          </code>
         </a>
         is
              enabled, the server prohibits client updates, even from
              users who have the
         <a class="link" href="privileges-provided.html#priv_connection-admin">
          <code class="literal">
           CONNECTION_ADMIN
          </code>
         </a>
         or
         <a class="link" href="privileges-provided.html#priv_super">
          <code class="literal">
           SUPER
          </code>
         </a>
         privilege.
        </p>
       </li>
       <li class="listitem">
        <p>
         Setting
         <a class="link" href="server-system-variables.html#sysvar_super_read_only">
          <code class="literal">
           super_read_only
          </code>
         </a>
         to
         <code class="literal">
          ON
         </code>
         implicitly forces
         <a class="link" href="server-system-variables.html#sysvar_read_only">
          <code class="literal">
           read_only
          </code>
         </a>
         to
         <code class="literal">
          ON
         </code>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         Setting
         <a class="link" href="server-system-variables.html#sysvar_read_only">
          <code class="literal">
           read_only
          </code>
         </a>
         to
         <code class="literal">
          OFF
         </code>
         implicitly forces
         <a class="link" href="server-system-variables.html#sysvar_super_read_only">
          <code class="literal">
           super_read_only
          </code>
         </a>
         to
         <code class="literal">
          OFF
         </code>
         .
        </p>
       </li>
      </ul>
     </div>
     <p>
      When
      <a class="link" href="server-system-variables.html#sysvar_read_only">
       <code class="literal">
        read_only
       </code>
      </a>
      is enabled and
          when
      <a class="link" href="server-system-variables.html#sysvar_super_read_only">
       <code class="literal">
        super_read_only
       </code>
      </a>
      is
          enabled, the server still permits these operations:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         Updates performed by replication threads, if the server is
              a replica. In replication setups, it can be useful to
              enable
         <a class="link" href="server-system-variables.html#sysvar_read_only">
          <code class="literal">
           read_only
          </code>
         </a>
         on
              replica servers to ensure that replicas accept updates
              only from the source server and not from clients.
        </p>
       </li>
       <li class="listitem">
        <p>
         Writes to the system table
         <code class="literal">
          mysql.gtid_executed
         </code>
         , which stores GTIDs
              for executed transactions that are not present in the
              current binary log file.
        </p>
       </li>
       <li class="listitem">
        <p>
         Use of
         <a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
          <code class="literal">
           ANALYZE TABLE
          </code>
         </a>
         or
         <a class="link" href="optimize-table.html" title="15.7.3.4 OPTIMIZE TABLE Statement">
          <code class="literal">
           OPTIMIZE TABLE
          </code>
         </a>
         statements.
              The purpose of read-only mode is to prevent changes to
              table structure or contents. Analysis and optimization do
              not qualify as such changes. This means, for example, that
              consistency checks on read-only replicas can be performed
              with
         <a class="link" href="mysqlcheck.html" title="6.5.3 mysqlcheck — A Table Maintenance Program">
          <span class="command">
           <strong>
            mysqlcheck
           </strong>
          </span>
         </a>
         <a class="link" href="mysqlcheck.html#option_mysqlcheck_all-databases">
          <code class="option">
           --all-databases
          </code>
         </a>
         <a class="link" href="mysqlcheck.html#option_mysqlcheck_analyze">
          <code class="option">
           --analyze
          </code>
         </a>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         Use of
         <a class="link" href="flush.html#flush-status">
          <code class="literal">
           FLUSH STATUS
          </code>
         </a>
         statements, which are always written to the binary log.
        </p>
       </li>
       <li class="listitem">
        <p>
         Operations on
         <code class="literal">
          TEMPORARY
         </code>
         tables.
        </p>
       </li>
       <li class="listitem">
        <p>
         Inserts into the log tables
              (
         <code class="literal">
          mysql.general_log
         </code>
         and
         <code class="literal">
          mysql.slow_log
         </code>
         ); see
         <a class="xref" href="log-destinations.html" title="7.4.1 Selecting General Query Log and Slow Query Log Output Destinations">
          Section 7.4.1, “Selecting General Query Log and Slow Query Log Output Destinations”
         </a>
         .
        </p>
       </li>
       <li class="listitem">
        <p>
         Updates to Performance Schema tables, such as
         <a class="link" href="update.html" title="15.2.17 UPDATE Statement">
          <code class="literal">
           UPDATE
          </code>
         </a>
         or
         <a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
          <code class="literal">
           TRUNCATE TABLE
          </code>
         </a>
         operations.
        </p>
       </li>
      </ul>
     </div>
     <p>
      Changes to
      <a class="link" href="server-system-variables.html#sysvar_read_only">
       <code class="literal">
        read_only
       </code>
      </a>
      on a
          replication source server are not replicated to replica
          servers. The value can be set on a replica independent of the
          setting on the source.
     </p>
     <p>
      The following conditions apply to attempts to enable
      <a class="link" href="server-system-variables.html#sysvar_read_only">
       <code class="literal">
        read_only
       </code>
      </a>
      (including implicit
          attempts resulting from enabling
      <a class="link" href="server-system-variables.html#sysvar_super_read_only">
       <code class="literal">
        super_read_only
       </code>
      </a>
      ):
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         The attempt fails and an error occurs if you have any
              explicit locks (acquired with
         <a class="link" href="lock-tables.html" title="15.3.6 LOCK TABLES and UNLOCK TABLES Statements">
          <code class="literal">
           LOCK
              TABLES
          </code>
         </a>
         ) or have a pending transaction.
        </p>
       </li>
       <li class="listitem">
        <p>
         The attempt blocks while other clients have any ongoing
              statement, active
         <code class="literal">
          LOCK TABLES WRITE
         </code>
         , or
              ongoing commit, until the locks are released and the
              statements and transactions end. While the attempt to
              enable
         <a class="link" href="server-system-variables.html#sysvar_read_only">
          <code class="literal">
           read_only
          </code>
         </a>
         is
              pending, requests by other clients for table locks or to
              begin transactions also block until
         <a class="link" href="server-system-variables.html#sysvar_read_only">
          <code class="literal">
           read_only
          </code>
         </a>
         has been set.
        </p>
       </li>
       <li class="listitem">
        <p>
         The attempt blocks if there are active transactions that
              hold metadata locks, until those transactions end.
        </p>
       </li>
       <li class="listitem">
        <p>
         <a class="link" href="server-system-variables.html#sysvar_read_only">
          <code class="literal">
           read_only
          </code>
         </a>
         can be enabled
              while you hold a global read lock (acquired with
         <a class="link" href="flush.html#flush-tables-with-read-lock">
          <code class="literal">
           FLUSH TABLES WITH READ
              LOCK
          </code>
         </a>
         ) because that does not involve table locks.
        </p>
       </li>
      </ul>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_read_rnd_buffer_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_read_rnd_buffer_size">
       <code class="literal">
        read_rnd_buffer_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270782832">
     </a>
     <a class="indexterm" name="idm46045270781792">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for read_rnd_buffer_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --read-rnd-buffer-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_read_rnd_buffer_size">
            read_rnd_buffer_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           262144
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2147483647
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable is used for reads from
      <code class="literal">
       MyISAM
      </code>
      tables, and, for any storage engine, for Multi-Range Read
          optimization.
     </p>
     <p>
      When reading rows from a
      <code class="literal">
       MyISAM
      </code>
      table in
          sorted order following a key-sorting operation, the rows are
          read through this buffer to avoid disk seeks. See
      <a class="xref" href="order-by-optimization.html" title="10.2.1.16 ORDER BY Optimization">
       Section 10.2.1.16, “ORDER BY Optimization”
      </a>
      . Setting the variable
          to a large value can improve
      <code class="literal">
       ORDER BY
      </code>
      performance by a lot. However, this is a buffer allocated for
          each client, so you should not set the global variable to a
          large value. Instead, change the session variable only from
          within those clients that need to run large queries.
     </p>
     <p>
      For more information about memory use during different
          operations, see
      <a class="xref" href="memory-use.html" title="10.12.3.1 How MySQL Uses Memory">
       Section 10.12.3.1, “How MySQL Uses Memory”
      </a>
      . For information
          about Multi-Range Read optimization, see
      <a class="xref" href="mrr-optimization.html" title="10.2.1.11 Multi-Range Read Optimization">
       Section 10.2.1.11, “Multi-Range Read Optimization”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_regexp_stack_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_regexp_stack_limit">
       <code class="literal">
        regexp_stack_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270744384">
     </a>
     <a class="indexterm" name="idm46045270743344">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for regexp_stack_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --regexp-stack-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_regexp_stack_limit">
            regexp_stack_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           8000000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2147483647
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum available memory in bytes for the internal stack
          used for regular expression matching operations performed by
      <a class="link" href="regexp.html#function_regexp-like">
       <code class="literal">
        REGEXP_LIKE()
       </code>
      </a>
      and similar
          functions (see
      <a class="xref" href="regexp.html" title="14.8.2 Regular Expressions">
       Section 14.8.2, “Regular Expressions”
      </a>
      ).
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_regexp_time_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_regexp_time_limit">
       <code class="literal">
        regexp_time_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270709792">
     </a>
     <a class="indexterm" name="idm46045270708752">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for regexp_time_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --regexp-time-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_regexp_time_limit">
            regexp_time_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           32
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2147483647
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The time limit for regular expression matching operations
          performed by
      <a class="link" href="regexp.html#function_regexp-like">
       <code class="literal">
        REGEXP_LIKE()
       </code>
      </a>
      and
          similar functions (see
      <a class="xref" href="regexp.html" title="14.8.2 Regular Expressions">
       Section 14.8.2, “Regular Expressions”
      </a>
      ). This limit
          is expressed as the maximum permitted number of steps
          performed by the match engine, and thus affects execution time
          only indirectly. Typically, it is on the order of
          milliseconds.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_require_row_format">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_require_row_format">
       <code class="literal">
        require_row_format
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270677120">
     </a>
     <a class="indexterm" name="idm46045270676080">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for require_row_format">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_require_row_format">
            require_row_format
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable is for internal server use by replication and
      <a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
       <span class="command">
        <strong>
         mysqlbinlog
        </strong>
       </span>
      </a>
      . It restricts DML events
          executed in the session to events encoded in row-based binary
          logging format only, and temporary tables cannot be created.
          Queries that do not respect the restrictions fail.
     </p>
     <p>
      Setting the session value of this system variable to
      <code class="literal">
       ON
      </code>
      requires no privileges. Setting the
          session value of this system variable to
      <code class="literal">
       OFF
      </code>
      is a restricted operation, and the
          session user must have privileges sufficient to set restricted
          session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_require_secure_transport">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_require_secure_transport">
       <code class="literal">
        require_secure_transport
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270649712">
     </a>
     <a class="indexterm" name="idm46045270648608">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for require_secure_transport">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --require-secure-transport[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_require_secure_transport">
            require_secure_transport
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether client connections to the server are required to use
          some form of secure transport. When this variable is enabled,
          the server permits only TCP/IP connections encrypted using
          TLS/SSL, or connections that use a socket file (on Unix) or
          shared memory (on Windows). The server rejects nonsecure
          connection attempts, which fail with an
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_secure_transport_required" target="_top">
       <code class="literal">
        ER_SECURE_TRANSPORT_REQUIRED
       </code>
      </a>
      error.
     </p>
     <p>
      This capability supplements per-account SSL requirements,
          which take precedence. For example, if an account is defined
          with
      <code class="literal">
       REQUIRE SSL
      </code>
      , enabling
      <a class="link" href="server-system-variables.html#sysvar_require_secure_transport">
       <code class="literal">
        require_secure_transport
       </code>
      </a>
      does
          not make it possible to use the account to connect using a
          Unix socket file.
     </p>
     <p>
      It is possible for a server to have no secure transports
          available. For example, a server on Windows supports no secure
          transports if started without specifying any SSL certificate
          or key files and with the
      <a class="link" href="server-system-variables.html#sysvar_shared_memory">
       <code class="literal">
        shared_memory
       </code>
      </a>
      system variable
          disabled. Under these conditions, attempts to enable
      <a class="link" href="server-system-variables.html#sysvar_require_secure_transport">
       <code class="literal">
        require_secure_transport
       </code>
      </a>
      at
          startup cause the server to write a message to the error log
          and exit. Attempts to enable the variable at runtime fail with
          an
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_no_secure_transports_configured" target="_top">
       <code class="literal">
        ER_NO_SECURE_TRANSPORTS_CONFIGURED
       </code>
      </a>
      error.
     </p>
     <p>
      See also
      <a class="xref" href="using-encrypted-connections.html#mandatory-encrypted-connections" title="Configuring Encrypted Connections as Mandatory">
       Configuring Encrypted Connections as Mandatory
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_restrict_fk_on_non_standard_key">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_restrict_fk_on_non_standard_key">
       <code class="literal">
        restrict_fk_on_non_standard_key
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270614032">
     </a>
     <a class="indexterm" name="idm46045270612928">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for restrict_fk_on_non_standard_key">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --restrict-fk-on-non-standard-key
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_restrict_fk_on_non_standard_key">
            restrict_fk_on_non_standard_key
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable, when
      <code class="literal">
       ON
      </code>
      (the default),
          prevents the use of non-unique keys or partial keys as foreign
          keys. To allow such keys to be used as foreign keys in the
          current session, use
      <code class="literal">
       SET
          @@session.restrict_fk_on_non_standard_key=OFF
      </code>
      ; to
          allow them to be used globally, set the global variable or
          start the server with
      <code class="option">
       --skip-restrict-fk-on-non-standard-key
      </code>
      .
     </p>
     <p>
      Using non-unique or partial keys as foreign keys in a
      <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
       <code class="literal">
        CREATE TABLE
       </code>
      </a>
      or
      <a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
       <code class="literal">
        ALTER TABLE
       </code>
      </a>
      statement is
          deprecated, and you should expect support for it to be removed
          in a future version of MySQL. When
      <code class="literal">
       restrict_fk_on_non_standard_key
      </code>
      is
      <code class="literal">
       ON
      </code>
      , attempts to do so are rejected with
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_fk_no_index_parent" target="_top">
       <code class="literal">
        ER_FK_NO_INDEX_PARENT
       </code>
      </a>
      ; when it
          is
      <code class="literal">
       OFF
      </code>
      , this usage is permitted but still
          raises
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_warn_deprecated_non_standard_key" target="_top">
       <code class="literal">
        ER_WARN_DEPRECATED_NON_STANDARD_KEY
       </code>
      </a>
      as a warning.
     </p>
     <p>
      <code class="literal">
       restrict_fk_on_non_standard_key
      </code>
      is
          deprecated, and subject to removal in a future version of
          MySQL. Setting it raises a deprecation warning.
     </p>
     <p>
      <b>
       Implication for MySQL Replication.
      </b>
      When a foreign key is created on a nonstandard key on the
            primary because
      <code class="literal">
       restrict_fk_on_non_standard_key
      </code>
      is
      <code class="literal">
       OFF
      </code>
      , the statement succeeds on the
            replica regardless of any setting on the replica for this
            variable.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_resultset_metadata">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_resultset_metadata">
       <code class="literal">
        resultset_metadata
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270572272">
     </a>
     <a class="indexterm" name="idm46045270571232">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for resultset_metadata">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_resultset_metadata">
            resultset_metadata
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           FULL
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            FULL
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            NONE
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      For connections for which metadata transfer is optional, the
          client sets the
      <a class="link" href="server-system-variables.html#sysvar_resultset_metadata">
       <code class="literal">
        resultset_metadata
       </code>
      </a>
      system
          variable to control whether the server returns result set
          metadata. Permitted values are
      <code class="literal">
       FULL
      </code>
      (return
          all metadata; this is the default) and
      <code class="literal">
       NONE
      </code>
      (return no metadata).
     </p>
     <p>
      For connections that are not metadata-optional, setting
      <a class="link" href="server-system-variables.html#sysvar_resultset_metadata">
       <code class="literal">
        resultset_metadata
       </code>
      </a>
      to
      <code class="literal">
       NONE
      </code>
      produces an error.
     </p>
     <p>
      For details about managing result set metadata transfer, see
      <a class="ulink" href="/doc/c-api/8.4/en/c-api-optional-metadata.html" target="_top">
       Optional Result Set Metadata
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_secondary_engine_cost_threshold">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_secondary_engine_cost_threshold">
       <code class="literal">
        secondary_engine_cost_threshold
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270538608">
     </a>
     <a class="indexterm" name="idm46045270537504">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for secondary_engine_cost_threshold">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_secondary_engine_cost_threshold">
            secondary_engine_cost_threshold
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Numeric
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           100000.000000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           DBL_MAX (maximum double value)
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The optimizer cost threshold for query offload to a secondary
          engine.
     </p>
     <p>
      For use with HeatWave. See
      <a class="ulink" href="/doc/heatwave/en/" target="_top">
       HeatWave User Guide
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_schema_definition_cache">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_schema_definition_cache">
       <code class="literal">
        schema_definition_cache
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270509200">
     </a>
     <a class="indexterm" name="idm46045270508160">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for schema_definition_cache">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --schema-definition-cache=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_schema_definition_cache">
            schema_definition_cache
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           256
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           256
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           524288
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Defines a limit for the number of schema definition objects,
          both used and unused, that can be kept in the dictionary
          object cache.
     </p>
     <p>
      Unused schema definition objects are only kept in the
          dictionary object cache when the number in use is less than
          the capacity defined by
      <code class="literal">
       schema_definition_cache
      </code>
      .
     </p>
     <p>
      A setting of
      <code class="literal">
       0
      </code>
      means that schema definition
          objects are only kept in the dictionary object cache while
          they are in use.
     </p>
     <p>
      For more information, see
      <a class="xref" href="data-dictionary-object-cache.html" title="16.4 Dictionary Object Cache">
       Section 16.4, “Dictionary Object Cache”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_secure_file_priv">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_secure_file_priv">
       <code class="literal">
        secure_file_priv
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270474960">
     </a>
     <a class="indexterm" name="idm46045270473872">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for secure_file_priv">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --secure-file-priv=dir_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_secure_file_priv">
            secure_file_priv
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           platform specific
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            empty string
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            dirname
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            NULL
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable is used to limit the effect of data import and
          export operations, such as those performed by the
      <a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
       <code class="literal">
        LOAD DATA
       </code>
      </a>
      and
      <a class="link" href="select-into.html" title="15.2.13.1 SELECT ... INTO Statement">
       <code class="literal">
        SELECT ... INTO
          OUTFILE
       </code>
      </a>
      statements and the
      <a class="link" href="string-functions.html#function_load-file">
       <code class="literal">
        LOAD_FILE()
       </code>
      </a>
      function. These
          operations are permitted only to users who have the
      <a class="link" href="privileges-provided.html#priv_file">
       <code class="literal">
        FILE
       </code>
      </a>
      privilege.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_secure_file_priv">
       <code class="literal">
        secure_file_priv
       </code>
      </a>
      may be set
          as follows:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         If empty, the variable has no effect. This is not a secure
              setting.
        </p>
       </li>
       <li class="listitem">
        <p>
         If set to the name of a directory, the server limits
              import and export operations to work only with files in
              that directory. The directory must exist; the server does
              not create it.
        </p>
       </li>
       <li class="listitem">
        <p>
         If set to
         <code class="literal">
          NULL
         </code>
         , the server disables
              import and export operations.
        </p>
       </li>
      </ul>
     </div>
     <p>
      The default value is platform specific and depends on the
          value of the
      <a class="link" href="source-configuration-options.html#option_cmake_install_layout">
       <code class="option">
        INSTALL_LAYOUT
       </code>
      </a>
      <span class="command">
       <strong>
        CMake
       </strong>
      </span>
      option, as shown in the following
          table. To specify the default
      <a class="link" href="server-system-variables.html#sysvar_secure_file_priv">
       <code class="literal">
        secure_file_priv
       </code>
      </a>
      value
          explicitly if you are building from source, use the
      <a class="link" href="source-configuration-options.html#option_cmake_install_secure_file_privdir">
       <code class="option">
        INSTALL_SECURE_FILE_PRIVDIR
       </code>
      </a>
      <span class="command">
       <strong>
        CMake
       </strong>
      </span>
      option.
     </p>
     <div class="informaltable">
      <table summary="The default secure_file_priv value for different INSTALL_LAYOUT values.">
       <colgroup>
        <col style="width: 35%"/>
        <col style="width: 65%"/>
       </colgroup>
       <thead>
        <tr>
         <th>
          <code class="literal">
           INSTALL_LAYOUT
          </code>
          Value
         </th>
         <th>
          Default
          <code class="literal">
           secure_file_priv
          </code>
          Value
         </th>
        </tr>
       </thead>
       <tbody>
        <tr>
         <td>
          <code class="literal">
           STANDALONE
          </code>
         </td>
         <td>
          empty
         </td>
        </tr>
        <tr>
         <td>
          <code class="literal">
           DEB
          </code>
          ,
          <code class="literal">
           RPM
          </code>
          ,
          <code class="literal">
           SVR4
          </code>
         </td>
         <td>
          <code class="filename">
           /var/lib/mysql-files
          </code>
         </td>
        </tr>
        <tr>
         <td>
          Otherwise
         </td>
         <td>
          <code class="filename">
           mysql-files
          </code>
          under the
          <a class="link" href="source-configuration-options.html#option_cmake_cmake_install_prefix">
           <code class="option">
            CMAKE_INSTALL_PREFIX
           </code>
          </a>
          value
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The server checks the value of
      <a class="link" href="server-system-variables.html#sysvar_secure_file_priv">
       <code class="literal">
        secure_file_priv
       </code>
      </a>
      at startup
          and writes a warning to the error log if the value is
          insecure. A non-
      <code class="literal">
       NULL
      </code>
      value is considered
          insecure if it is empty, or the value is the data directory or
          a subdirectory of it, or a directory that is accessible by all
          users. If
      <a class="link" href="server-system-variables.html#sysvar_secure_file_priv">
       <code class="literal">
        secure_file_priv
       </code>
      </a>
      is
          set to a nonexistent path, the server writes an error message
          to the error log and exits.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_select_into_buffer_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_select_into_buffer_size">
       <code class="literal">
        select_into_buffer_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270407472">
     </a>
     <a class="indexterm" name="idm46045270406400">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for select_into_buffer_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --select-into-buffer-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_select_into_buffer_size">
            select_into_buffer_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           131072
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           8192
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2147479552
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           4096
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      When using
      <a class="link" href="select-into.html" title="15.2.13.1 SELECT ... INTO Statement">
       <code class="literal">
        SELECT
          INTO OUTFILE
       </code>
      </a>
      or
      <code class="literal">
       SELECT INTO
          DUMPFILE
      </code>
      to dump data into one or more files for
          backup creation, data migration, or other purposes, writes can
          often be buffered and then trigger a large burst of write I/O
          activity to the disk or other storage device and stall other
          queries that are more sensitive to latency. You can use this
          variable to control the size of the buffer used to write data
          to the storage device to determine when buffer synchronization
          should occur, and thus to prevent write stalls of the kind
          just described from occurring.
     </p>
     <p>
      <code class="literal">
       select_into_buffer_size
      </code>
      overrides any value
          set for
      <a class="link" href="server-system-variables.html#sysvar_read_buffer_size">
       <code class="literal">
        read_buffer_size
       </code>
      </a>
      .
          (
      <code class="literal">
       select_into_buffer_size
      </code>
      and
      <code class="literal">
       read_buffer_size
      </code>
      have the same default,
          maximum, and minimum values.) You can also use
      <a class="link" href="server-system-variables.html#sysvar_select_into_disk_sync_delay">
       <code class="literal">
        select_into_disk_sync_delay
       </code>
      </a>
      to set a timeout to be observed afterwards, each time
          synchronization takes place.
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_select_into_disk_sync">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_select_into_disk_sync">
       <code class="literal">
        select_into_disk_sync
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270362800">
     </a>
     <a class="indexterm" name="idm46045270361728">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for select_into_disk_sync">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --select-into-disk-sync={ON|OFF}
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_select_into_disk_sync">
            select_into_disk_sync
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            OFF
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            ON
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      When set on
      <code class="literal">
       ON
      </code>
      , enables buffer
          synchronization of writes to an output file by a long-running
      <a class="link" href="select-into.html" title="15.2.13.1 SELECT ... INTO Statement">
       <code class="literal">
        SELECT INTO
          OUTFILE
       </code>
      </a>
      or
      <code class="literal">
       SELECT INTO DUMPFILE
      </code>
      statement using
      <a class="link" href="server-system-variables.html#sysvar_select_into_buffer_size">
       <code class="literal">
        select_into_buffer_size
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_select_into_disk_sync_delay">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_select_into_disk_sync_delay">
       <code class="literal">
        select_into_disk_sync_delay
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270329488">
     </a>
     <a class="indexterm" name="idm46045270328400">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for select_into_disk_sync_delay">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --select-into-disk-sync-delay=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_select_into_disk_sync_delay">
            select_into_disk_sync_delay
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          milliseconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      When buffer synchronization of writes to an output file by a
          long-running
      <a class="link" href="select-into.html" title="15.2.13.1 SELECT ... INTO Statement">
       <code class="literal">
        SELECT INTO
          OUTFILE
       </code>
      </a>
      or
      <code class="literal">
       SELECT INTO DUMPFILE
      </code>
      statement is enabled by
      <a class="link" href="server-system-variables.html#sysvar_select_into_disk_sync">
       <code class="literal">
        select_into_disk_sync
       </code>
      </a>
      , this
          variable sets an optional delay (in milliseconds) following
          synchronization.
      <code class="literal">
       0
      </code>
      (the default) means no
          delay.
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_session_track_gtids">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_session_track_gtids">
       <code class="literal">
        session_track_gtids
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270291392">
     </a>
     <a class="indexterm" name="idm46045270290352">
     </a>
     <a class="indexterm" name="idm46045270288864">
     </a>
     <a class="indexterm" name="idm46045270287776">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for session_track_gtids">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --session-track-gtids=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_session_track_gtids">
            session_track_gtids
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            OFF
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            OWN_GTID
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            ALL_GTIDS
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Controls whether the server returns GTIDs to the client,
          enabling the client to use them to track the server state.
          Depending on the variable value, at the end of executing each
          transaction, the server’s GTIDs are captured and returned to
          the client as part of the acknowledgement. The possible values
          for
      <a class="link" href="server-system-variables.html#sysvar_session_track_gtids">
       <code class="literal">
        session_track_gtids
       </code>
      </a>
      are
          as follows:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          OFF
         </code>
         : The server does not return GTIDs
              to the client. This is the default.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          OWN_GTID
         </code>
         : The server returns the GTIDs
              for all transactions that were successfully committed by
              this client in its current session since the last
              acknowledgement. Typically, this is the single GTID for
              the last transaction committed, but if a single client
              request resulted in multiple transactions, the server
              returns a GTID set containing all the relevant GTIDs.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ALL_GTIDS
         </code>
         : The server returns the
              global value of its
         <a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
          <code class="literal">
           gtid_executed
          </code>
         </a>
         system
              variable, which it reads at a point after the transaction
              is successfully committed. As well as the GTID for the
              transaction just committed, this GTID set includes all
              transactions committed on the server by any client, and
              can include transactions committed after the point when
              the transaction currently being acknowledged was
              committed.
        </p>
       </li>
      </ul>
     </div>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_session_track_gtids">
       <code class="literal">
        session_track_gtids
       </code>
      </a>
      cannot be
          set within transactional context.
     </p>
     <p>
      For more information about session state tracking, see
      <a class="xref" href="session-state-tracking.html" title="7.1.18 Server Tracking of Client Session State">
       Section 7.1.18, “Server Tracking of Client Session State”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_session_track_schema">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_session_track_schema">
       <code class="literal">
        session_track_schema
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270246336">
     </a>
     <a class="indexterm" name="idm46045270245296">
     </a>
     <a class="indexterm" name="idm46045270243808">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for session_track_schema">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --session-track-schema[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_session_track_schema">
            session_track_schema
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Controls whether the server tracks when the default schema
          (database) is set within the current session and notifies the
          client to make the schema name available.
     </p>
     <p>
      If the schema name tracker is enabled, name notification
          occurs each time the default schema is set, even if the new
          schema name is the same as the old.
     </p>
     <p>
      For more information about session state tracking, see
      <a class="xref" href="session-state-tracking.html" title="7.1.18 Server Tracking of Client Session State">
       Section 7.1.18, “Server Tracking of Client Session State”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_session_track_state_change">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_session_track_state_change">
       <code class="literal">
        session_track_state_change
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270217808">
     </a>
     <a class="indexterm" name="idm46045270216704">
     </a>
     <a class="indexterm" name="idm46045270215200">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for session_track_state_change">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --session-track-state-change[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_session_track_state_change">
            session_track_state_change
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Controls whether the server tracks changes to the state of the
          current session and notifies the client when state changes
          occur. Changes can be reported for these attributes of client
          session state:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         The default schema (database).
        </p>
       </li>
       <li class="listitem">
        <p>
         Session-specific values for system variables.
        </p>
       </li>
       <li class="listitem">
        <p>
         User-defined variables.
        </p>
       </li>
       <li class="listitem">
        <p>
         Temporary tables.
        </p>
       </li>
       <li class="listitem">
        <p>
         Prepared statements.
        </p>
       </li>
      </ul>
     </div>
     <p>
      If the session state tracker is enabled, notification occurs
          for each change that involves tracked session attributes, even
          if the new attribute values are the same as the old. For
          example, setting a user-defined variable to its current value
          results in a notification.
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_session_track_state_change">
       <code class="literal">
        session_track_state_change
       </code>
      </a>
      variable controls only notification of when changes occur, not
          what the changes are. For example, state-change notifications
          occur when the default schema is set or tracked session system
          variables are assigned, but the notification does not include
          the schema name or variable values. To receive notification of
          the schema name or session system variable values, use the
      <a class="link" href="server-system-variables.html#sysvar_session_track_schema">
       <code class="literal">
        session_track_schema
       </code>
      </a>
      or
      <a class="link" href="server-system-variables.html#sysvar_session_track_system_variables">
       <code class="literal">
        session_track_system_variables
       </code>
      </a>
      system variable, respectively.
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       Assigning a value to
       <a class="link" href="server-system-variables.html#sysvar_session_track_state_change">
        <code class="literal">
         session_track_state_change
        </code>
       </a>
       itself is not considered a state change and is not reported
            as such. However, if its name listed in the value of
       <a class="link" href="server-system-variables.html#sysvar_session_track_system_variables">
        <code class="literal">
         session_track_system_variables
        </code>
       </a>
       ,
            any assignments to it do result in notification of the new
            value.
      </p>
     </div>
     <p>
      For more information about session state tracking, see
      <a class="xref" href="session-state-tracking.html" title="7.1.18 Server Tracking of Client Session State">
       Section 7.1.18, “Server Tracking of Client Session State”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_session_track_system_variables">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_session_track_system_variables">
       <code class="literal">
        session_track_system_variables
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270176064">
     </a>
     <a class="indexterm" name="idm46045270174960">
     </a>
     <a class="indexterm" name="idm46045270173456">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for session_track_system_variables">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --session-track-system-variables=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_session_track_system_variables">
            session_track_system_variables
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           time_zone, autocommit, character_set_client, character_set_results, character_set_connection
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Controls whether the server tracks assignments to session
          system variables and notifies the client of the name and value
          of each assigned variable. The variable value is a
          comma-separated list of variables for which to track
          assignments. By default, notification is enabled for
      <a class="link" href="server-system-variables.html#sysvar_time_zone">
       <code class="literal">
        time_zone
       </code>
      </a>
      ,
      <a class="link" href="server-system-variables.html#sysvar_autocommit">
       <code class="literal">
        autocommit
       </code>
      </a>
      ,
      <a class="link" href="server-system-variables.html#sysvar_character_set_client">
       <code class="literal">
        character_set_client
       </code>
      </a>
      ,
      <a class="link" href="server-system-variables.html#sysvar_character_set_results">
       <code class="literal">
        character_set_results
       </code>
      </a>
      , and
      <a class="link" href="server-system-variables.html#sysvar_character_set_connection">
       <code class="literal">
        character_set_connection
       </code>
      </a>
      .
          (The latter three variables are those affected by
      <a class="link" href="set-names.html" title="15.7.6.3 SET NAMES Statement">
       <code class="literal">
        SET NAMES
       </code>
      </a>
      .)
     </p>
     <p>
      To enable display of the Statement ID for each statement
          processed, use the
      <code class="literal">
       statement_id
      </code>
      variable.
          For example:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa91062243"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql&gt;</span>  <span class="token keyword">SET</span> <span class="token variable">@@SESSION.session_track_system_variables</span><span class="token operator">=</span><span class="token string">'statement_id'</span>
<span class="token prompt">mysql&gt;</span>  <span class="token keyword">SELECT</span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.0006 sec)</span>
Statement ID: <span class="token number">603835</span></code></pre>
     </div>
     <p>
      The special value
      <code class="literal">
       *
      </code>
      (asterisk) causes the
          server to track assignments to all session variables. If
          given, this value must be specified by itself without specific
          system variable names. This value also enables display of the
          Statement ID for each successful statement processed.
     </p>
     <p>
      To disable notification of session variable assignments, set
      <a class="link" href="server-system-variables.html#sysvar_session_track_system_variables">
       <code class="literal">
        session_track_system_variables
       </code>
      </a>
      to the empty string.
     </p>
     <p>
      If session system variable tracking is enabled, notification
          occurs for all assignments to tracked session variables, even
          if the new values are the same as the old.
     </p>
     <p>
      For more information about session state tracking, see
      <a class="xref" href="session-state-tracking.html" title="7.1.18 Server Tracking of Client Session State">
       Section 7.1.18, “Server Tracking of Client Session State”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_session_track_transaction_info">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_session_track_transaction_info">
       <code class="literal">
        session_track_transaction_info
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270133664">
     </a>
     <a class="indexterm" name="idm46045270132560">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for session_track_transaction_info">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --session-track-transaction-info=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_session_track_transaction_info">
            session_track_transaction_info
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            OFF
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            STATE
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            CHARACTERISTICS
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Controls whether the server tracks the state and
          characteristics of transactions within the current session and
          notifies the client to make this information available. These
      <a class="link" href="server-system-variables.html#sysvar_session_track_transaction_info">
       <code class="literal">
        session_track_transaction_info
       </code>
      </a>
      values are permitted:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          OFF
         </code>
         : Disable transaction state
              tracking. This is the default.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          STATE
         </code>
         : Enable transaction state
              tracking without characteristics tracking. State tracking
              enables the client to determine whether a transaction is
              in progress and whether it could be moved to a different
              session without being rolled back.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          CHARACTERISTICS
         </code>
         : Enable transaction
              state tracking, including characteristics tracking.
              Characteristics tracking enables the client to determine
              how to restart a transaction in another session so that it
              has the same characteristics as in the original session.
              The following characteristics are relevant for this
              purpose:
        </p>
        <div class="copytoclipboard-wrapper">
         <pre class="programlisting language-simple"><div class="docs-select-all right" id="sa53872801"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">ISOLATION LEVEL
READ ONLY
READ WRITE
WITH CONSISTENT SNAPSHOT</code></pre>
        </div>
       </li>
      </ul>
     </div>
     <p>
      For a client to safely relocate a transaction to another
          session, it must track not only transaction state but also
          transaction characteristics. In addition, the client must
          track the
      <a class="link" href="server-system-variables.html#sysvar_transaction_isolation">
       <code class="literal">
        transaction_isolation
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
       <code class="literal">
        transaction_read_only
       </code>
      </a>
      system
          variables to correctly determine the session defaults. (To
          track these variables, list them in the value of the
      <a class="link" href="server-system-variables.html#sysvar_session_track_system_variables">
       <code class="literal">
        session_track_system_variables
       </code>
      </a>
      system variable.)
     </p>
     <p>
      For more information about session state tracking, see
      <a class="xref" href="session-state-tracking.html" title="7.1.18 Server Tracking of Client Session State">
       Section 7.1.18, “Server Tracking of Client Session State”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_set_operations_buffer_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_set_operations_buffer_size">
       <code class="literal">
        set_operations_buffer_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270089440">
     </a>
     <a class="indexterm" name="idm46045270088336">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for set_operations_buffer_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --set-operations-buffer-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_set_operations_buffer_size">
            set_operations_buffer_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           256K
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           16K
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           1 GB
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Sets the buffer size for
      <a class="link" href="intersect.html" title="15.2.8 INTERSECT Clause">
       <code class="literal">
        INTERSECT
       </code>
      </a>
      and
      <a class="link" href="except.html" title="15.2.4 EXCEPT Clause">
       <code class="literal">
        EXCEPT
       </code>
      </a>
      operations that use hash
          tables when the
      <a class="link" href="switchable-optimizations.html#optflag_hash-set-operations">
       <code class="literal">
        hash_set_operations
       </code>
      </a>
      optimizer switch is
      <code class="literal">
       ON
      </code>
      . In general,
          increasing the size of this buffer improves performance of
          these operations when the hashing optimization is enabled.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sha256_password_auto_generate_rsa_keys">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sha256_password_auto_generate_rsa_keys">
       <code class="literal">
        sha256_password_auto_generate_rsa_keys
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270054144">
     </a>
     <a class="indexterm" name="idm46045270053104">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sha256_password_auto_generate_rsa_keys">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --sha256-password-auto-generate-rsa-keys[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sha256_password_auto_generate_rsa_keys">
            sha256_password_auto_generate_rsa_keys
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The server uses this variable to determine whether to
          autogenerate RSA private/public key-pair files in the data
          directory if they do not already exist.
     </p>
     <p>
      At startup, the server automatically generates RSA
          private/public key-pair files in the data directory if all of
          these conditions are true: The
      <a class="link" href="server-system-variables.html#sysvar_sha256_password_auto_generate_rsa_keys">
       <code class="literal">
        sha256_password_auto_generate_rsa_keys
       </code>
      </a>
      or
      <a class="link" href="server-system-variables.html#sysvar_caching_sha2_password_auto_generate_rsa_keys">
       <code class="literal">
        caching_sha2_password_auto_generate_rsa_keys
       </code>
      </a>
      system variable is enabled; no RSA options are specified; the
          RSA files are missing from the data directory. These key-pair
          files enable secure password exchange using RSA over
          unencrypted connections for accounts authenticated by the
      <code class="literal">
       sha256_password
      </code>
      (deprecated) or
      <code class="literal">
       caching_sha2_password
      </code>
      plugin; see
      <a class="xref" href="sha256-pluggable-authentication.html" title="8.4.1.3 SHA-256 Pluggable Authentication">
       Section 8.4.1.3, “SHA-256 Pluggable Authentication”
      </a>
      , and
      <a class="xref" href="caching-sha2-pluggable-authentication.html" title="8.4.1.2 Caching SHA-2 Pluggable Authentication">
       Section 8.4.1.2, “Caching SHA-2 Pluggable Authentication”
      </a>
      .
     </p>
     <p>
      For more information about RSA file autogeneration, including
          file names and characteristics, see
      <a class="xref" href="creating-ssl-rsa-files-using-mysql.html" title="8.3.3.1 Creating SSL and RSA Certificates and Keys using MySQL">
       Section 8.3.3.1, “Creating SSL and RSA Certificates and Keys using MySQL”
      </a>
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_auto_generate_certs">
       <code class="literal">
        auto_generate_certs
       </code>
      </a>
      system variable is related but controls autogeneration of SSL
          certificate and key files needed for secure connections using
          SSL.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sha256_password_private_key_path">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sha256_password_private_key_path">
       <code class="literal">
        sha256_password_private_key_path
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045270016928">
     </a>
     <a class="indexterm" name="idm46045270015824">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sha256_password_private_key_path">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --sha256-password-private-key-path=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sha256_password_private_key_path">
            sha256_password_private_key_path
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           private_key.pem
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The value of this variable is the path name of the RSA private
          key file for the
      <code class="literal">
       sha256_password
      </code>
      (deprecated) authentication plugin. If the file is named as a
          relative path, it is interpreted relative to the server data
          directory. The file must be in PEM format.
     </p>
     <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Important
      </div>
      <p>
       Because this file stores a private key, its access mode
            should be restricted so that only the MySQL server can read
            it.
      </p>
     </div>
     <p>
      For information about
      <code class="literal">
       sha256_password
      </code>
      , see
      <a class="xref" href="sha256-pluggable-authentication.html" title="8.4.1.3 SHA-256 Pluggable Authentication">
       Section 8.4.1.3, “SHA-256 Pluggable Authentication”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sha256_password_proxy_users">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sha256_password_proxy_users">
       <code class="literal">
        sha256_password_proxy_users
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269985456">
     </a>
     <a class="indexterm" name="idm46045269984352">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sha256_password_proxy_users">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --sha256-password-proxy-users[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sha256_password_proxy_users">
            sha256_password_proxy_users
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls whether the
      <code class="literal">
       sha256_password
      </code>
      (deprecated) built-in
          authentication plugin supports proxy users. It has no effect
          unless the
      <a class="link" href="server-system-variables.html#sysvar_check_proxy_users">
       <code class="literal">
        check_proxy_users
       </code>
      </a>
      system variable is enabled. For information about user
          proxying, see
      <a class="xref" href="proxy-users.html" title="8.2.19 Proxy Users">
       Section 8.2.19, “Proxy Users”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sha256_password_public_key_path">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sha256_password_public_key_path">
       <code class="literal">
        sha256_password_public_key_path
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269954928">
     </a>
     <a class="indexterm" name="idm46045269953824">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sha256_password_public_key_path">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --sha256-password-public-key-path=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sha256_password_public_key_path">
            sha256_password_public_key_path
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           public_key.pem
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The value of this variable is the path name of the RSA public
          key file for the
      <code class="literal">
       sha256_password
      </code>
      (deprecated) authentication plugin. If the file is named as a
          relative path, it is interpreted relative to the server data
          directory. The file must be in PEM format. Because this file
          stores a public key, copies can be freely distributed to
          client users. (Clients that explicitly specify a public key
          when connecting to the server using RSA password encryption
          must use the same public key as that used by the server.)
     </p>
     <p>
      For information about
      <code class="literal">
       sha256_password
      </code>
      (deprecated), including information about how clients specify
          the RSA public key, see
      <a class="xref" href="sha256-pluggable-authentication.html" title="8.4.1.3 SHA-256 Pluggable Authentication">
       Section 8.4.1.3, “SHA-256 Pluggable Authentication”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_shared_memory">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_shared_memory">
       <code class="literal">
        shared_memory
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269924032">
     </a>
     <a class="indexterm" name="idm46045269922944">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for shared_memory">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --shared-memory[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_shared_memory">
            shared_memory
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Platform Specific
         </th>
         <td>
          Windows
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      (Windows only.) Whether the server permits shared-memory
          connections.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_shared_memory_base_name">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_shared_memory_base_name">
       <code class="literal">
        shared_memory_base_name
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269896288">
     </a>
     <a class="indexterm" name="idm46045269895248">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for shared_memory_base_name">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --shared-memory-base-name=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_shared_memory_base_name">
            shared_memory_base_name
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Platform Specific
         </th>
         <td>
          Windows
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           MYSQL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      (Windows only.) The name of shared memory to use for
          shared-memory connections. This is useful when running
          multiple MySQL instances on a single physical machine. The
          default name is
      <code class="literal">
       MYSQL
      </code>
      . The name is
          case-sensitive.
     </p>
     <p>
      This variable applies only if the server is started with the
      <a class="link" href="server-system-variables.html#sysvar_shared_memory">
       <code class="literal">
        shared_memory
       </code>
      </a>
      system variable
          enabled to support shared-memory connections.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_show_create_table_skip_secondary_engine">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_show_create_table_skip_secondary_engine">
       <code class="literal">
        show_create_table_skip_secondary_engine
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269865776">
     </a>
     <a class="indexterm" name="idm46045269864736">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for show_create_table_skip_secondary_engine">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --show-create-table-skip-secondary-engine[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_show_create_table_skip_secondary_engine">
            show_create_table_skip_secondary_engine
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Enabling
      <a class="link" href="server-system-variables.html#sysvar_show_create_table_skip_secondary_engine">
       <code class="literal">
        show_create_table_skip_secondary_engine
       </code>
      </a>
      causes the
      <code class="literal">
       SECONDARY ENGINE
      </code>
      clause to be
          excluded from
      <a class="link" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement">
       <code class="literal">
        SHOW CREATE TABLE
       </code>
      </a>
      output, and from
      <a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
       <code class="literal">
        CREATE TABLE
       </code>
      </a>
      statements dumped by the
      <a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
       <span class="command">
        <strong>
         mysqldump
        </strong>
       </span>
      </a>
      utility.
     </p>
     <p>
      <a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
       <span class="command">
        <strong>
         mysqldump
        </strong>
       </span>
      </a>
      provides the
      <a class="link" href="mysqldump.html#option_mysqldump_show-create-skip-secondary-engine">
       <code class="option">
        --show-create-skip-secondary-engine
       </code>
      </a>
      option. When specified, it enables the
      <a class="link" href="server-system-variables.html#sysvar_show_create_table_skip_secondary_engine">
       <code class="literal">
        show_create_table_skip_secondary_engine
       </code>
      </a>
      system variable for the duration of the dump operation.
     </p>
     <p>
      For use with HeatWave. See
      <a class="ulink" href="/doc/heatwave/en/" target="_top">
       HeatWave User Guide
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_show_create_table_verbosity">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_show_create_table_verbosity">
       <code class="literal">
        show_create_table_verbosity
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269829120">
     </a>
     <a class="indexterm" name="idm46045269828016">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for show_create_table_verbosity">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --show-create-table-verbosity[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_show_create_table_verbosity">
            show_create_table_verbosity
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      <a class="link" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement">
       <code class="literal">
        SHOW CREATE TABLE
       </code>
      </a>
      normally does
          not show the
      <code class="literal">
       ROW_FORMAT
      </code>
      table option if the
          row format is the default format. Enabling this variable
          causes
      <a class="link" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement">
       <code class="literal">
        SHOW CREATE TABLE
       </code>
      </a>
      to
          display
      <code class="literal">
       ROW_FORMAT
      </code>
      regardless of whether it
          is the default format.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_show_gipk_in_create_table_and_information_schema">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_show_gipk_in_create_table_and_information_schema">
       <code class="literal">
        show_gipk_in_create_table_and_information_schema
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269799312">
     </a>
     <a class="indexterm" name="idm46045269798192">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for show_gipk_in_create_table_and_information_schema">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --show-gipk-in-create-table-and-information-schema[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_show_gipk_in_create_table_and_information_schema">
            show_gipk_in_create_table_and_information_schema
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether generated invisible primary keys are visible in the
          output of
      <a class="link" href="show.html" title="15.7.7 SHOW Statements">
       <code class="literal">
        SHOW
       </code>
      </a>
      statements and
          in Information Schema tables. When this variable is set to
      <code class="literal">
       OFF
      </code>
      , such keys are not shown.
     </p>
     <p>
      This variable is not replicated.
     </p>
     <p>
      For more information, see
      <a class="xref" href="create-table-gipks.html" title="15.1.20.11 Generated Invisible Primary Keys">
       Section 15.1.20.11, “Generated Invisible Primary Keys”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_skip_external_locking">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_skip_external_locking">
       <code class="literal">
        skip_external_locking
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269769872">
     </a>
     <a class="indexterm" name="idm46045269768800">
     </a>
     <a class="indexterm" name="idm46045269767312">
     </a>
     <a class="indexterm" name="idm46045269766272">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for skip_external_locking">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --skip-external-locking[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_skip_external_locking">
            skip_external_locking
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This is
      <code class="literal">
       OFF
      </code>
      if
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      uses external locking (system locking),
      <code class="literal">
       ON
      </code>
      if external locking is disabled. This affects only
      <a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine">
       <code class="literal">
        MyISAM
       </code>
      </a>
      table access.
     </p>
     <p>
      This variable is set by the
      <a class="link" href="server-options.html#option_mysqld_external-locking">
       <code class="option">
        --external-locking
       </code>
      </a>
      or
      <a class="link" href="server-options.html#option_mysqld_external-locking">
       <code class="option">
        --skip-external-locking
       </code>
      </a>
      option. External locking is disabled by default.
     </p>
     <p>
      External locking affects only
      <a class="link" href="myisam-storage-engine.html" title="18.2 The MyISAM Storage Engine">
       <code class="literal">
        MyISAM
       </code>
      </a>
      table access. For more
          information, including conditions under which it can and
          cannot be used, see
      <a class="xref" href="external-locking.html" title="10.11.5 External Locking">
       Section 10.11.5, “External Locking”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_skip_name_resolve">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_skip_name_resolve">
       <code class="literal">
        skip_name_resolve
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269732896">
     </a>
     <a class="indexterm" name="idm46045269731856">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for skip_name_resolve">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --skip-name-resolve[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_skip_name_resolve">
            skip_name_resolve
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether to resolve host names when checking client
          connections. If this variable is
      <code class="literal">
       OFF
      </code>
      ,
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      resolves host names when checking
          client connections. If it is
      <code class="literal">
       ON
      </code>
      ,
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      uses only IP numbers; in this case,
          all
      <code class="literal">
       Host
      </code>
      column values in the grant tables
          must be IP addresses. See
      <a class="xref" href="host-cache.html" title="7.1.12.3 DNS Lookups and the Host Cache">
       Section 7.1.12.3, “DNS Lookups and the Host Cache”
      </a>
      .
     </p>
     <p>
      Depending on the network configuration of your system and the
      <code class="literal">
       Host
      </code>
      values for your accounts, clients may
          need to connect using an explicit
      <a class="link" href="connection-options.html#option_general_host">
       <code class="option">
        --host
       </code>
      </a>
      option, such as
      <a class="link" href="connection-options.html#option_general_host">
       <code class="option">
        --host=127.0.0.1
       </code>
      </a>
      or
      <a class="link" href="connection-options.html#option_general_host">
       <code class="option">
        --host=::1
       </code>
      </a>
      .
     </p>
     <a class="indexterm" name="idm46045269700160">
     </a>
     <p>
      An attempt to connect to the host
      <code class="literal">
       127.0.0.1
      </code>
      normally resolves to the
      <code class="literal">
       localhost
      </code>
      account.
          However, this fails if the server is run with
      <a class="link" href="server-system-variables.html#sysvar_skip_name_resolve">
       <code class="literal">
        skip_name_resolve
       </code>
      </a>
      enabled. If
          you plan to do that, make sure an account exists that can
          accept a connection. For example, to be able to connect as
      <code class="literal">
       root
      </code>
      using
      <a class="link" href="connection-options.html#option_general_host">
       <code class="option">
        --host=127.0.0.1
       </code>
      </a>
      or
      <a class="link" href="connection-options.html#option_general_host">
       <code class="option">
        --host=::1
       </code>
      </a>
      , create these
          accounts:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa50995778"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'root'</span>@<span class="token string">'127.0.0.1'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">root-password</em>'</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'root'</span>@<span class="token string">'::1'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">root-password</em>'</span><span class="token punctuation">;</span></code></pre>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_skip_networking">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_skip_networking">
       <code class="literal">
        skip_networking
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269688784">
     </a>
     <a class="indexterm" name="idm46045269687696">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for skip_networking">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --skip-networking[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_skip_networking">
            skip_networking
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls whether the server permits TCP/IP
          connections. By default, it is disabled (permit TCP
          connections). If enabled, the server permits only local
          (non-TCP/IP) connections and all interaction with
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      must be made using named pipes or
          shared memory (on Windows) or Unix socket files (on Unix).
          This option is highly recommended for systems where only local
          clients are permitted. See
      <a class="xref" href="host-cache.html" title="7.1.12.3 DNS Lookups and the Host Cache">
       Section 7.1.12.3, “DNS Lookups and the Host Cache”
      </a>
      .
     </p>
     <p>
      Because starting the server with
      <a class="link" href="server-options.html#option_mysqld_skip-grant-tables">
       <code class="option">
        --skip-grant-tables
       </code>
      </a>
      disables
          authentication checks, the server also disables remote
          connections in that case by enabling
      <a class="link" href="server-system-variables.html#sysvar_skip_networking">
       <code class="literal">
        skip_networking
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_skip_show_database">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_skip_show_database">
       <code class="literal">
        skip_show_database
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269658096">
     </a>
     <a class="indexterm" name="idm46045269657056">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for skip-show-database">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --skip-show-database
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_skip_show_database">
            skip_show_database
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This prevents people from using the
      <a class="link" href="show-databases.html" title="15.7.7.15 SHOW DATABASES Statement">
       <code class="literal">
        SHOW
          DATABASES
       </code>
      </a>
      statement if they do not have the
      <a class="link" href="privileges-provided.html#priv_show-databases">
       <code class="literal">
        SHOW DATABASES
       </code>
      </a>
      privilege. This
          can improve security if you have concerns about users being
          able to see databases belonging to other users. Its effect
          depends on the
      <a class="link" href="privileges-provided.html#priv_show-databases">
       <code class="literal">
        SHOW DATABASES
       </code>
      </a>
      privilege: If the variable value is
      <code class="literal">
       ON
      </code>
      , the
      <a class="link" href="show-databases.html" title="15.7.7.15 SHOW DATABASES Statement">
       <code class="literal">
        SHOW DATABASES
       </code>
      </a>
      statement is
          permitted only to users who have the
      <a class="link" href="privileges-provided.html#priv_show-databases">
       <code class="literal">
        SHOW
          DATABASES
       </code>
      </a>
      privilege, and the statement displays all
          database names. If the value is
      <code class="literal">
       OFF
      </code>
      ,
      <a class="link" href="show-databases.html" title="15.7.7.15 SHOW DATABASES Statement">
       <code class="literal">
        SHOW DATABASES
       </code>
      </a>
      is permitted to
          all users, but displays the names of only those databases for
          which the user has the
      <a class="link" href="privileges-provided.html#priv_show-databases">
       <code class="literal">
        SHOW
          DATABASES
       </code>
      </a>
      or other privilege.
     </p>
     <div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Caution
      </div>
      <p>
       Because any static global privilege is considered a
            privilege for all databases, any static global privilege
            enables a user to see all database names with
       <a class="link" href="show-databases.html" title="15.7.7.15 SHOW DATABASES Statement">
        <code class="literal">
         SHOW DATABASES
        </code>
       </a>
       or by
            examining the
       <a class="link" href="information-schema-schemata-table.html" title="28.3.31 The INFORMATION_SCHEMA SCHEMATA Table">
        <code class="literal">
         SCHEMATA
        </code>
       </a>
       table of
       <code class="literal">
        INFORMATION_SCHEMA
       </code>
       , except databases that
            have been restricted at the database level by partial
            revokes.
      </p>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_slow_launch_time">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_slow_launch_time">
       <code class="literal">
        slow_launch_time
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269617456">
     </a>
     <a class="indexterm" name="idm46045269616368">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for slow_launch_time">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --slow-launch-time=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_slow_launch_time">
            slow_launch_time
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           2
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If creating a thread takes longer than this many seconds, the
          server increments the
      <a class="link" href="server-status-variables.html#statvar_Slow_launch_threads">
       <code class="literal">
        Slow_launch_threads
       </code>
      </a>
      status
          variable.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_slow_query_log">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_slow_query_log">
       <code class="literal">
        slow_query_log
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269583680">
     </a>
     <a class="indexterm" name="idm46045269582592">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for slow_query_log">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --slow-query-log[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_slow_query_log">
            slow_query_log
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether the slow query log is enabled. The value can be 0 (or
      <code class="literal">
       OFF
      </code>
      ) to disable the log or 1 (or
      <code class="literal">
       ON
      </code>
      ) to enable the log. The destination for
          log output is controlled by the
      <a class="link" href="server-system-variables.html#sysvar_log_output">
       <code class="literal">
        log_output
       </code>
      </a>
      system variable;
          if that value is
      <code class="literal">
       NONE
      </code>
      , no log entries are
          written even if the log is enabled.
     </p>
     <p>
      <span class="quote">
       “
       <span class="quote">
        Slow
       </span>
       ”
      </span>
      is determined by the value of the
      <a class="link" href="server-system-variables.html#sysvar_long_query_time">
       <code class="literal">
        long_query_time
       </code>
      </a>
      variable. See
      <a class="xref" href="slow-query-log.html" title="7.4.5 The Slow Query Log">
       Section 7.4.5, “The Slow Query Log”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_slow_query_log_file">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_slow_query_log_file">
       <code class="literal">
        slow_query_log_file
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269551744">
     </a>
     <a class="indexterm" name="idm46045269550704">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for slow_query_log_file">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --slow-query-log-file=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_slow_query_log_file">
            slow_query_log_file
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           host_name-slow.log
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The name of the slow query log file. The default value is
      <code class="filename">
       <em class="replaceable">
        <code>
         host_name
        </code>
       </em>
       -slow.log
      </code>
      ,
          but the initial value can be changed with the
      <code class="literal">
       --slow_query_log_file
      </code>
      option.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_socket">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_socket">
       <code class="literal">
        socket
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269524448">
     </a>
     <a class="indexterm" name="idm46045269523376">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for socket">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --socket={file_name|pipe_name}
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_socket">
            socket
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Windows)
         </th>
         <td>
          <code class="literal">
           MySQL
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Default Value (Other)
         </th>
         <td>
          <code class="literal">
           /tmp/mysql.sock
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      On Unix platforms, this variable is the name of the socket
          file that is used for local client connections. The default is
      <code class="filename">
       /tmp/mysql.sock
      </code>
      . (For some distribution
          formats, the directory might be different, such as
      <code class="filename">
       /var/lib/mysql
      </code>
      for RPMs.)
     </p>
     <p>
      On Windows, this variable is the name of the named pipe that
          is used for local client connections. The default value is
      <code class="literal">
       MySQL
      </code>
      (not case-sensitive).
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sort_buffer_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sort_buffer_size">
       <code class="literal">
        sort_buffer_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269493552">
     </a>
     <a class="indexterm" name="idm46045269492464">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sort_buffer_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --sort-buffer-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sort_buffer_size">
            sort_buffer_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           262144
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           32768
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Windows)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Other, 64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Other, 32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294967295
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Each session that must perform a sort allocates a buffer of
          this size.
      <a class="link" href="server-system-variables.html#sysvar_sort_buffer_size">
       <code class="literal">
        sort_buffer_size
       </code>
      </a>
      is not specific to any storage engine and applies in a general
          manner for optimization. At minimum the
      <a class="link" href="server-system-variables.html#sysvar_sort_buffer_size">
       <code class="literal">
        sort_buffer_size
       </code>
      </a>
      value must
          be large enough to accommodate fifteen tuples in the sort
          buffer. Also, increasing the value of
      <a class="link" href="server-system-variables.html#sysvar_max_sort_length">
       <code class="literal">
        max_sort_length
       </code>
      </a>
      may require
          increasing the value of
      <a class="link" href="server-system-variables.html#sysvar_sort_buffer_size">
       <code class="literal">
        sort_buffer_size
       </code>
      </a>
      . For more
          information, see
      <a class="xref" href="order-by-optimization.html" title="10.2.1.16 ORDER BY Optimization">
       Section 10.2.1.16, “ORDER BY Optimization”
      </a>
     </p>
     <p>
      If you see many
      <a class="link" href="server-status-variables.html#statvar_Sort_merge_passes">
       <code class="literal">
        Sort_merge_passes
       </code>
      </a>
      per second
          in
      <a class="link" href="show-status.html" title="15.7.7.37 SHOW STATUS Statement">
       <code class="literal">
        SHOW GLOBAL
          STATUS
       </code>
      </a>
      output, you can consider increasing the
      <a class="link" href="server-system-variables.html#sysvar_sort_buffer_size">
       <code class="literal">
        sort_buffer_size
       </code>
      </a>
      value to
          speed up
      <code class="literal">
       ORDER BY
      </code>
      or
      <code class="literal">
       GROUP
          BY
      </code>
      operations that cannot be improved with query
          optimization or improved indexing.
     </p>
     <p>
      The optimizer tries to work out how much space is needed but
          can allocate more, up to the limit. Setting it larger than
          required globally slows down most queries that perform sorts.
          It is best to increase it as a session setting, and only for
          the sessions that need a larger size. On Linux, there are
          thresholds of 256KB and 2MB where larger values may
          significantly slow down memory allocation, so you should
          consider staying below one of those values. Experiment to find
          the best value for your workload. See
      <a class="xref" href="temporary-files.html" title="B.3.3.5 Where MySQL Stores Temporary Files">
       Section B.3.3.5, “Where MySQL Stores Temporary Files”
      </a>
      .
     </p>
     <p>
      The maximum permissible setting for
      <a class="link" href="server-system-variables.html#sysvar_sort_buffer_size">
       <code class="literal">
        sort_buffer_size
       </code>
      </a>
      is
          4GB−1. Larger values are permitted for 64-bit platforms
          (except 64-bit Windows, for which large values are truncated
          to 4GB−1 with a warning).
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_auto_is_null">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_auto_is_null">
       <code class="literal">
        sql_auto_is_null
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269440704">
     </a>
     <a class="indexterm" name="idm46045269439616">
     </a>
     <a class="indexterm" name="idm46045269438128">
     </a>
     <a class="indexterm" name="idm46045269437056">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql_auto_is_null">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_auto_is_null">
            sql_auto_is_null
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If this variable is enabled, then after a statement that
          successfully inserts an automatically generated
      <code class="literal">
       AUTO_INCREMENT
      </code>
      value, you can find that
          value by issuing a statement of the following form:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa2798368"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> <em class="replaceable">tbl_name</em> <span class="token keyword">WHERE</span> <em class="replaceable">auto_col</em> <span class="token operator">IS</span> <span class="token boolean">NULL</span></code></pre>
     </div>
     <p>
      If the statement returns a row, the value returned is the same
          as if you invoked the
      <a class="link" href="information-functions.html#function_last-insert-id">
       <code class="literal">
        LAST_INSERT_ID()
       </code>
      </a>
      function. For
          details, including the return value after a multiple-row
          insert, see
      <a class="xref" href="information-functions.html" title="14.15 Information Functions">
       Section 14.15, “Information Functions”
      </a>
      . If no
      <code class="literal">
       AUTO_INCREMENT
      </code>
      value was successfully
          inserted, the
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      statement
          returns no row.
     </p>
     <p>
      The behavior of retrieving an
      <code class="literal">
       AUTO_INCREMENT
      </code>
      value by using an
      <a class="link" href="comparison-operators.html#operator_is-null">
       <code class="literal">
        IS NULL
       </code>
      </a>
      comparison is used by
          some ODBC programs, such as Access. See
      <a class="ulink" href="/doc/connector-odbc/en/connector-odbc-usagenotes-functionality-last-insert-id.html" target="_top">
       Obtaining Auto-Increment Values
      </a>
      .
          This behavior can be disabled by setting
      <a class="link" href="server-system-variables.html#sysvar_sql_auto_is_null">
       <code class="literal">
        sql_auto_is_null
       </code>
      </a>
      to
      <code class="literal">
       OFF
      </code>
      .
     </p>
     <p>
      The default value of
      <a class="link" href="server-system-variables.html#sysvar_sql_auto_is_null">
       <code class="literal">
        sql_auto_is_null
       </code>
      </a>
      is
      <code class="literal">
       OFF
      </code>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_big_selects">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_big_selects">
       <code class="literal">
        sql_big_selects
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269400256">
     </a>
     <a class="indexterm" name="idm46045269399168">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql_big_selects">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_big_selects">
            sql_big_selects
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If set to
      <code class="literal">
       OFF
      </code>
      , MySQL aborts
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      statements that are
          likely to take a very long time to execute (that is,
          statements for which the optimizer estimates that the number
          of examined rows exceeds the value of
      <a class="link" href="server-system-variables.html#sysvar_max_join_size">
       <code class="literal">
        max_join_size
       </code>
      </a>
      ). This is
          useful when an inadvisable
      <code class="literal">
       WHERE
      </code>
      statement
          has been issued. The default value for a new connection is
      <code class="literal">
       ON
      </code>
      , which permits all
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      statements.
     </p>
     <p>
      If you set the
      <a class="link" href="server-system-variables.html#sysvar_max_join_size">
       <code class="literal">
        max_join_size
       </code>
      </a>
      system variable to a value other than
      <code class="literal">
       DEFAULT
      </code>
      ,
      <a class="link" href="server-system-variables.html#sysvar_sql_big_selects">
       <code class="literal">
        sql_big_selects
       </code>
      </a>
      is set to
      <code class="literal">
       OFF
      </code>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_buffer_result">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_buffer_result">
       <code class="literal">
        sql_buffer_result
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269366688">
     </a>
     <a class="indexterm" name="idm46045269365648">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql_buffer_result">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_buffer_result">
            sql_buffer_result
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If enabled,
      <a class="link" href="server-system-variables.html#sysvar_sql_buffer_result">
       <code class="literal">
        sql_buffer_result
       </code>
      </a>
      forces results from
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      statements to be put into temporary tables. This helps MySQL
          free the table locks early and can be beneficial in cases
          where it takes a long time to send results to the client. The
          default value is
      <code class="literal">
       OFF
      </code>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_generate_invisible_primary_key">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_generate_invisible_primary_key">
       <code class="literal">
        sql_generate_invisible_primary_key
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269340096">
     </a>
     <a class="indexterm" name="idm46045269339008">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql_generate_invisible_primary_key">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --sql-generate-invisible-primary-key[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_generate_invisible_primary_key">
            sql_generate_invisible_primary_key
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether this server adds a generated invisible primary key to
          any
      <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
       <code class="literal">
        InnoDB
       </code>
      </a>
      table that is created
          without one.
     </p>
     <p>
      This variable is not replicated. In addition, even if set on
          the replica, it is ignored by replication applier threads;
          this means that, by default, a replica does not generate a
          primary key for any replicated table which, on the source, was
          created without one. You can cause the replica to generate
          invisible primary keys for such tables by setting
      <code class="literal">
       REQUIRE_TABLE_PRIMARY_KEY_CHECK = GENERATE
      </code>
      as part of a
      <a class="link" href="change-replication-source-to.html" title="15.4.2.2 CHANGE REPLICATION SOURCE TO Statement">
       <code class="literal">
        CHANGE REPLICATION SOURCE
          TO
       </code>
      </a>
      statement, optionally specifying a replication
          channel.
     </p>
     <p>
      For more information and examples, see
      <a class="xref" href="create-table-gipks.html" title="15.1.20.11 Generated Invisible Primary Keys">
       Section 15.1.20.11, “Generated Invisible Primary Keys”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_log_off">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_log_off">
       <code class="literal">
        sql_log_off
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269309136">
     </a>
     <a class="indexterm" name="idm46045269308048">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql_log_off">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_log_off">
            sql_log_off
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            OFF
           </code>
           (enable logging)
          </p>
          <p class="valid-value">
           <code class="literal">
            ON
           </code>
           (disable logging)
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls whether logging to the general query
          log is disabled for the current session (assuming that the
          general query log itself is enabled). The default value is
      <code class="literal">
       OFF
      </code>
      (that is, enable logging). To disable
          or enable general query logging for the current session, set
          the session
      <a class="link" href="server-system-variables.html#sysvar_sql_log_off">
       <code class="literal">
        sql_log_off
       </code>
      </a>
      variable to
      <code class="literal">
       ON
      </code>
      or
      <code class="literal">
       OFF
      </code>
      .
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_mode">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_mode">
       <code class="literal">
        sql_mode
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269277104">
     </a>
     <a class="indexterm" name="idm46045269276016">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql-mode">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --sql-mode=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_mode">
            sql_mode
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Set
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ONLY_FULL_GROUP_BY STRICT_TRANS_TABLES NO_ZERO_IN_DATE NO_ZERO_DATE ERROR_FOR_DIVISION_BY_ZERO NO_ENGINE_SUBSTITUTION
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            ALLOW_INVALID_DATES
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            ANSI_QUOTES
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            ERROR_FOR_DIVISION_BY_ZERO
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            HIGH_NOT_PRECEDENCE
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            IGNORE_SPACE
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            NO_AUTO_VALUE_ON_ZERO
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            NO_BACKSLASH_ESCAPES
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            NO_DIR_IN_CREATE
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            NO_ENGINE_SUBSTITUTION
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            NO_UNSIGNED_SUBTRACTION
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            NO_ZERO_DATE
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            NO_ZERO_IN_DATE
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            ONLY_FULL_GROUP_BY
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            PAD_CHAR_TO_FULL_LENGTH
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            PIPES_AS_CONCAT
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            REAL_AS_FLOAT
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            STRICT_ALL_TABLES
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            STRICT_TRANS_TABLES
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            TIME_TRUNCATE_FRACTIONAL
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The current server SQL mode, which can be set dynamically. For
          details, see
      <a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
       Section 7.1.11, “Server SQL Modes”
      </a>
      .
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       MySQL installation programs may configure the SQL mode
            during the installation process.
      </p>
      <p>
       If the SQL mode differs from the default or from what you
            expect, check for a setting in an option file that the
            server reads at startup.
      </p>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_notes">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_notes">
       <code class="literal">
        sql_notes
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269229184">
     </a>
     <a class="indexterm" name="idm46045269228096">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql_notes">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_notes">
            sql_notes
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If enabled (the default), diagnostics of
      <code class="literal">
       Note
      </code>
      level increment
      <code class="literal">
       warning_count
      </code>
      and the server records them.
          If disabled,
      <code class="literal">
       Note
      </code>
      diagnostics do not
          increment
      <a class="link" href="server-system-variables.html#sysvar_warning_count">
       <code class="literal">
        warning_count
       </code>
      </a>
      and
          the server does not record them.
      <a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
       <span class="command">
        <strong>
         mysqldump
        </strong>
       </span>
      </a>
      includes output to disable this variable so that reloading the
          dump file does not produce warnings for events that do not
          affect the integrity of the reload operation.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_quote_show_create">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_quote_show_create">
       <code class="literal">
        sql_quote_show_create
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269201120">
     </a>
     <a class="indexterm" name="idm46045269200080">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql_quote_show_create">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_quote_show_create">
            sql_quote_show_create
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If enabled (the default), the server quotes identifiers for
      <a class="link" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement">
       <code class="literal">
        SHOW CREATE TABLE
       </code>
      </a>
      and
      <a class="link" href="show-create-database.html" title="15.7.7.7 SHOW CREATE DATABASE Statement">
       <code class="literal">
        SHOW CREATE DATABASE
       </code>
      </a>
      statements. If disabled, quoting is disabled. This option is
          enabled by default so that replication works for identifiers
          that require quoting. See
      <a class="xref" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement">
       Section 15.7.7.11, “SHOW CREATE TABLE Statement”
      </a>
      ,
          and
      <a class="xref" href="show-create-database.html" title="15.7.7.7 SHOW CREATE DATABASE Statement">
       Section 15.7.7.7, “SHOW CREATE DATABASE Statement”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_require_primary_key">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_require_primary_key">
       <code class="literal">
        sql_require_primary_key
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269173776">
     </a>
     <a class="indexterm" name="idm46045269172736">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql_require_primary_key">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --sql-require-primary-key[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_require_primary_key">
            sql_require_primary_key
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether statements that create new tables or alter the
          structure of existing tables enforce the requirement that
          tables have a primary key.
     </p>
     <p>
      Setting the session value of this system variable is a
          restricted operation. The session user must have privileges
          sufficient to set restricted session variables. See
      <a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
       Section 7.1.9.1, “System Variable Privileges”
      </a>
      .
     </p>
     <p>
      Enabling this variable helps avoid performance problems in
          row-based replication that can occur when tables have no
          primary key. Suppose that a table has no primary key and an
          update or delete modifies multiple rows. On the replication
          source server, this operation can be performed using a single
          table scan but, when replicated using row-based replication,
          results in a table scan for each row to be modified on the
          replica. With a primary key, these table scans do not occur.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_sql_require_primary_key">
       <code class="literal">
        sql_require_primary_key
       </code>
      </a>
      applies to both base tables and
      <code class="literal">
       TEMPORARY
      </code>
      tables, and changes to its value are replicated to replica
          servers. The table must use MySQL storage engines that can
          participate in replication.
     </p>
     <p>
      When enabled,
      <a class="link" href="server-system-variables.html#sysvar_sql_require_primary_key">
       <code class="literal">
        sql_require_primary_key
       </code>
      </a>
      has
          these effects:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         Attempts to create a new table with no primary key fail
              with an error. This includes
         <code class="literal">
          CREATE TABLE ...
              LIKE
         </code>
         . It also includes
         <code class="literal">
          CREATE TABLE ...
              SELECT
         </code>
         , unless the
         <code class="literal">
          CREATE
              TABLE
         </code>
         part includes a primary key definition.
        </p>
       </li>
       <li class="listitem">
        <p>
         Attempts to drop the primary key from an existing table
              fail with an error, with the exception that dropping the
              primary key and adding a primary key in the same
         <code class="literal">
          ALTER TABLE
         </code>
         statement is permitted.
        </p>
        <p>
         Dropping the primary key fails even if the table also
              contains a
         <code class="literal">
          UNIQUE NOT NULL
         </code>
         index.
        </p>
       </li>
       <li class="listitem">
        <p>
         Attempts to import a table with no primary key fail with
              an error.
        </p>
       </li>
      </ul>
     </div>
     <p>
      The
      <code class="literal">
       REQUIRE_TABLE_PRIMARY_KEY_CHECK
      </code>
      option
          of the
      <a class="link" href="change-replication-source-to.html" title="15.4.2.2 CHANGE REPLICATION SOURCE TO Statement">
       <code class="literal">
        CHANGE REPLICATION SOURCE
          TO
       </code>
      </a>
      statement enables a replica to select its own
          policy for primary key checks. When the option is set to
      <code class="literal">
       ON
      </code>
      for a replication channel, the replica
          always uses the value
      <code class="literal">
       ON
      </code>
      for the
      <a class="link" href="server-system-variables.html#sysvar_sql_require_primary_key">
       <code class="literal">
        sql_require_primary_key
       </code>
      </a>
      system variable in replication operations, requiring a primary
          key. When the option is set to
      <code class="literal">
       OFF
      </code>
      , the
          replica always uses the value
      <code class="literal">
       OFF
      </code>
      for the
      <a class="link" href="server-system-variables.html#sysvar_sql_require_primary_key">
       <code class="literal">
        sql_require_primary_key
       </code>
      </a>
      system variable in replication operations, so that a primary
          key is never required, even if the source required one. When
          the
      <code class="literal">
       REQUIRE_TABLE_PRIMARY_KEY_CHECK
      </code>
      option
          is set to
      <code class="literal">
       STREAM
      </code>
      , which is the default, the
          replica uses whatever value is replicated from the source for
          each transaction. With the
      <code class="literal">
       STREAM
      </code>
      setting
          for the
      <code class="literal">
       REQUIRE_TABLE_PRIMARY_KEY_CHECK
      </code>
      option, if privilege checks are in use for the replication
          channel, the
      <code class="literal">
       PRIVILEGE_CHECKS_USER
      </code>
      account
          needs privileges sufficient to set restricted session
          variables, so that it can set the session value for the
      <a class="link" href="server-system-variables.html#sysvar_sql_require_primary_key">
       <code class="literal">
        sql_require_primary_key
       </code>
      </a>
      system variable. With the
      <code class="literal">
       ON
      </code>
      or
      <code class="literal">
       OFF
      </code>
      settings, the account does not need
          these privileges. For more information, see
      <a class="xref" href="replication-privilege-checks.html" title="19.3.3 Replication Privilege Checks">
       Section 19.3.3, “Replication Privilege Checks”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_safe_updates">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_safe_updates">
       <code class="literal">
        sql_safe_updates
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269118560">
     </a>
     <a class="indexterm" name="idm46045269117472">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql_safe_updates">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_safe_updates">
            sql_safe_updates
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If this variable is enabled,
      <a class="link" href="update.html" title="15.2.17 UPDATE Statement">
       <code class="literal">
        UPDATE
       </code>
      </a>
      and
      <a class="link" href="delete.html" title="15.2.2 DELETE Statement">
       <code class="literal">
        DELETE
       </code>
      </a>
      statements that do not
          use a key in the
      <code class="literal">
       WHERE
      </code>
      clause or a
      <code class="literal">
       LIMIT
      </code>
      clause produce an error. This makes
          it possible to catch
      <a class="link" href="update.html" title="15.2.17 UPDATE Statement">
       <code class="literal">
        UPDATE
       </code>
      </a>
      and
      <a class="link" href="delete.html" title="15.2.2 DELETE Statement">
       <code class="literal">
        DELETE
       </code>
      </a>
      statements where keys
          are not used properly and that would probably change or delete
          a large number of rows. The default value is
      <code class="literal">
       OFF
      </code>
      .
     </p>
     <p>
      For the
      <a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
       <span class="command">
        <strong>
         mysql
        </strong>
       </span>
      </a>
      client,
      <a class="link" href="server-system-variables.html#sysvar_sql_safe_updates">
       <code class="literal">
        sql_safe_updates
       </code>
      </a>
      can be
          enabled by using the
      <a class="link" href="mysql-command-options.html#option_mysql_safe-updates">
       <code class="option">
        --safe-updates
       </code>
      </a>
      option. For more
          information, see
      <a class="xref" href="mysql-tips.html#safe-updates" title="Using Safe-Updates Mode (--safe-updates)">
       Using Safe-Updates Mode (--safe-updates)
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_select_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_select_limit">
       <code class="literal">
        sql_select_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269083664">
     </a>
     <a class="indexterm" name="idm46045269082576">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql_select_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_select_limit">
            sql_select_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum number of rows to return from
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      statements. For more
          information, see
      <a class="xref" href="mysql-tips.html#safe-updates" title="Using Safe-Updates Mode (--safe-updates)">
       Using Safe-Updates Mode (--safe-updates)
      </a>
      .
     </p>
     <p>
      The default value for a new connection is the maximum number
          of rows that the server permits per table. Typical default
          values are (2
      <sup>
       32
      </sup>
      )−1 or
          (2
      <sup>
       64
      </sup>
      )−1. If you have changed
          the limit, the default value can be restored by assigning a
          value of
      <code class="literal">
       DEFAULT
      </code>
      .
     </p>
     <p>
      If a
      <a class="link" href="select.html" title="15.2.13 SELECT Statement">
       <code class="literal">
        SELECT
       </code>
      </a>
      has a
      <code class="literal">
       LIMIT
      </code>
      clause, the
      <code class="literal">
       LIMIT
      </code>
      takes precedence over the value of
      <a class="link" href="server-system-variables.html#sysvar_sql_select_limit">
       <code class="literal">
        sql_select_limit
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_sql_warnings">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_sql_warnings">
       <code class="literal">
        sql_warnings
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269047008">
     </a>
     <a class="indexterm" name="idm46045269045920">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for sql_warnings">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_sql_warnings">
            sql_warnings
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls whether single-row
      <a class="link" href="insert.html" title="15.2.7 INSERT Statement">
       <code class="literal">
        INSERT
       </code>
      </a>
      statements produce an
          information string if warnings occur. The default is
      <code class="literal">
       OFF
      </code>
      . Set the value to
      <code class="literal">
       ON
      </code>
      to produce an information string.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ssl_ca">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ssl_ca">
       <code class="literal">
        ssl_ca
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045269021200">
     </a>
     <a class="indexterm" name="idm46045269020128">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ssl_ca">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ssl-ca=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ssl_ca">
            ssl_ca
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The path name of the Certificate Authority (CA) certificate
          file in PEM format. The file contains a list of trusted SSL
          Certificate Authorities.
     </p>
     <p>
      This variable can be modified at runtime to affect the TLS
          context the server uses for new connections established after
          the execution of
      <a class="link" href="alter-instance.html#alter-instance-reload-tls">
       <code class="literal">
        ALTER INSTANCE RELOAD
          TLS
       </code>
      </a>
      or after a restart if the variable value was
          persisted. See
      <a class="xref" href="using-encrypted-connections.html#using-encrypted-connections-server-side-runtime-configuration" title="Server-Side Runtime Configuration and Monitoring for Encrypted Connections">
       Server-Side Runtime Configuration and Monitoring for Encrypted
        Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ssl_capath">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ssl_capath">
       <code class="literal">
        ssl_capath
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268992656">
     </a>
     <a class="indexterm" name="idm46045268991568">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ssl_capath">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ssl-capath=dir_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ssl_capath">
            ssl_capath
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Directory name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The path name of the directory that contains trusted SSL
          Certificate Authority (CA) certificate files in PEM format.
     </p>
     <p>
      This variable is can be modified at runtime to affect the TLS
          context the server uses for new connections established after
          the execution of
      <a class="link" href="alter-instance.html#alter-instance-reload-tls">
       <code class="literal">
        ALTER INSTANCE RELOAD
          TLS
       </code>
      </a>
      or after a restart if the variable value was
          persisted. See
      <a class="xref" href="using-encrypted-connections.html#using-encrypted-connections-server-side-runtime-configuration" title="Server-Side Runtime Configuration and Monitoring for Encrypted Connections">
       Server-Side Runtime Configuration and Monitoring for Encrypted
        Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ssl_cert">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ssl_cert">
       <code class="literal">
        ssl_cert
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268964384">
     </a>
     <a class="indexterm" name="idm46045268963296">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ssl_cert">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ssl-cert=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ssl_cert">
            ssl_cert
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The path name of the server SSL public key certificate file in
          PEM format.
     </p>
     <p>
      If the server is started with
      <a class="link" href="server-system-variables.html#sysvar_ssl_cert">
       <code class="literal">
        ssl_cert
       </code>
      </a>
      set to a certificate
          that uses any restricted cipher or cipher category, the server
          starts with support for encrypted connections disabled. For
          information about cipher restrictions, see
      <a class="xref" href="encrypted-connection-protocols-ciphers.html#encrypted-connection-cipher-configuration" title="Connection Cipher Configuration">
       Connection Cipher Configuration
      </a>
      .
     </p>
     <p>
      This variable can be modified at runtime to affect the TLS
          context the server uses for new connections established after
          the execution of
      <a class="link" href="alter-instance.html#alter-instance-reload-tls">
       <code class="literal">
        ALTER INSTANCE RELOAD
          TLS
       </code>
      </a>
      or after a restart if the variable value was
          persisted. See
      <a class="xref" href="using-encrypted-connections.html#using-encrypted-connections-server-side-runtime-configuration" title="Server-Side Runtime Configuration and Monitoring for Encrypted Connections">
       Server-Side Runtime Configuration and Monitoring for Encrypted
        Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ssl_cipher">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ssl_cipher">
       <code class="literal">
        ssl_cipher
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268933360">
     </a>
     <a class="indexterm" name="idm46045268932272">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ssl_cipher">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ssl-cipher=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ssl_cipher">
            ssl_cipher
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The list of permissible encryption ciphers for connections
          that use TLSv1.2. If no cipher in the list is supported,
          encrypted connections that use this TLS protocol do not work.
     </p>
     <p>
      The list may include any of the following values:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-ECDSA-AES128-GCM-SHA256
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-ECDSA-AES256-GCM-SHA384
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-RSA-AES128-GCM-SHA256
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-RSA-AES256-GCM-SHA384
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-ECDSA-CHACHA20-POLY1305
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-RSA-CHACHA20-POLY1305
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-ECDSA-AES256-CCM
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ECDHE-ECDSA-AES128-CCM
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          DHE-RSA-AES128-GCM-SHA256
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          DHE-RSA-AES256-GCM-SHA384
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          DHE-RSA-AES256-CCM
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          DHE-RSA-AES128-CCM
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          DHE-RSA-CHACHA20-POLY1305
         </code>
        </p>
       </li>
      </ul>
     </div>
     <p>
      Trying to include any values in the cipher list that are not
          shown here when setting this variable raises an error
          (
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_blocked_cipher" target="_top">
       <code class="literal">
        ER_BLOCKED_CIPHER
       </code>
      </a>
      ).
     </p>
     <p>
      For greatest portability, the cipher list should be a list of
          one or more cipher names, separated by colons. The following
          example shows two cipher names separated by a colon:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa78468210"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token punctuation">[</span>mysqld<span class="token punctuation">]</span>
ssl_cipher=<span class="token atrule">"DHE-RSA-AES128-GCM-SHA256:AES128-SHA"</span></code></pre>
     </div>
     <p>
      OpenSSL supports the syntax for specifying ciphers described
          in the OpenSSL documentation at
      <a class="ulink" href="https://www.openssl.org/docs/manmaster/man1/ciphers.html" target="_blank">
       https://www.openssl.org/docs/manmaster/man1/ciphers.html
      </a>
      .
     </p>
     <p>
      For information about which encryption ciphers MySQL supports,
          see
      <a class="xref" href="encrypted-connection-protocols-ciphers.html" title="8.3.2 Encrypted Connection TLS Protocols and Ciphers">
       Section 8.3.2, “Encrypted Connection TLS Protocols and Ciphers”
      </a>
      .
     </p>
     <p>
      This variable can be modified at runtime to affect the TLS
          context the server uses for new connections established after
          the execution of
      <a class="link" href="alter-instance.html#alter-instance-reload-tls">
       <code class="literal">
        ALTER INSTANCE RELOAD
          TLS
       </code>
      </a>
      or after a restart if the variable value was
          persisted. See
      <a class="xref" href="using-encrypted-connections.html#using-encrypted-connections-server-side-runtime-configuration" title="Server-Side Runtime Configuration and Monitoring for Encrypted Connections">
       Server-Side Runtime Configuration and Monitoring for Encrypted
        Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ssl_crl">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ssl_crl">
       <code class="literal">
        ssl_crl
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268879328">
     </a>
     <a class="indexterm" name="idm46045268878256">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ssl_crl">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ssl-crl=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ssl_crl">
            ssl_crl
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The path name of the file containing certificate revocation
          lists in PEM format.
     </p>
     <p>
      This variable can be modified at runtime to affect the TLS
          context the server uses for new connections established after
          the execution of
      <a class="link" href="alter-instance.html#alter-instance-reload-tls">
       <code class="literal">
        ALTER INSTANCE RELOAD
          TLS
       </code>
      </a>
      or after a restart if the variable value was
          persisted. See
      <a class="xref" href="using-encrypted-connections.html#using-encrypted-connections-server-side-runtime-configuration" title="Server-Side Runtime Configuration and Monitoring for Encrypted Connections">
       Server-Side Runtime Configuration and Monitoring for Encrypted
        Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ssl_crlpath">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ssl_crlpath">
       <code class="literal">
        ssl_crlpath
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268851120">
     </a>
     <a class="indexterm" name="idm46045268850032">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ssl_crlpath">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ssl-crlpath=dir_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ssl_crlpath">
            ssl_crlpath
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Directory name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The path of the directory that contains certificate
          revocation-list files in PEM format.
     </p>
     <p>
      This variable can be modified at runtime to affect the TLS
          context the server uses for new connections established after
          the execution of
      <a class="link" href="alter-instance.html#alter-instance-reload-tls">
       <code class="literal">
        ALTER INSTANCE RELOAD
          TLS
       </code>
      </a>
      or after a restart if the variable value was
          persisted. See
      <a class="xref" href="using-encrypted-connections.html#using-encrypted-connections-server-side-runtime-configuration" title="Server-Side Runtime Configuration and Monitoring for Encrypted Connections">
       Server-Side Runtime Configuration and Monitoring for Encrypted
        Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ssl_fips_mode">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ssl_fips_mode">
       <code class="literal">
        ssl_fips_mode
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268822880">
     </a>
     <a class="indexterm" name="idm46045268821792">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ssl_fips_mode">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ssl-fips-mode={OFF|ON|STRICT}
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ssl_fips_mode">
            ssl_fips_mode
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            OFF
           </code>
           (or 0)
          </p>
          <p class="valid-value">
           <code class="literal">
            ON
           </code>
           (or 1)
          </p>
          <p class="valid-value">
           <code class="literal">
            STRICT
           </code>
           (or 2)
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Controls whether to enable FIPS mode on the server side. The
      <a class="link" href="server-system-variables.html#sysvar_ssl_fips_mode">
       <code class="literal">
        ssl_fips_mode
       </code>
      </a>
      system variable
          differs from other
      <code class="literal">
       ssl_
       <em class="replaceable">
        <code>
         xxx
        </code>
       </em>
      </code>
      system
          variables in that it is not used to control whether the server
          permits encrypted connections, but rather to affect which
          cryptographic operations are permitted. See
      <a class="xref" href="fips-mode.html" title="8.8 FIPS Support">
       Section 8.8, “FIPS Support”
      </a>
      .
     </p>
     <p>
      These
      <a class="link" href="server-system-variables.html#sysvar_ssl_fips_mode">
       <code class="literal">
        ssl_fips_mode
       </code>
      </a>
      values
          are permitted:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          OFF
         </code>
         (or 0): Disable FIPS mode.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ON
         </code>
         (or 1): Enable FIPS mode.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          STRICT
         </code>
         (or 2): Enable
         <span class="quote">
          “
          <span class="quote">
           strict
          </span>
          ”
         </span>
         FIPS mode.
        </p>
       </li>
      </ul>
     </div>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       If the OpenSSL FIPS Object Module is not available, the only
            permitted value for
       <a class="link" href="server-system-variables.html#sysvar_ssl_fips_mode">
        <code class="literal">
         ssl_fips_mode
        </code>
       </a>
       is
       <code class="literal">
        OFF
       </code>
       . In this case, setting
       <a class="link" href="server-system-variables.html#sysvar_ssl_fips_mode">
        <code class="literal">
         ssl_fips_mode
        </code>
       </a>
       to
       <code class="literal">
        ON
       </code>
       or
       <code class="literal">
        STRICT
       </code>
       at
            startup causes the server to produce an error message and
            exit.
      </p>
     </div>
     <p>
      This option is deprecated and made read-only. Expect it to be
          removed in a future version of MySQL.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ssl_key">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ssl_key">
       <code class="literal">
        ssl_key
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268774000">
     </a>
     <a class="indexterm" name="idm46045268772928">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ssl_key">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ssl-key=file_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ssl_key">
            ssl_key
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          File name
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The path name of the server SSL private key file in PEM
          format. For better security, use a certificate with an RSA key
          size of at least 2048 bits.
     </p>
     <p>
      If the key file is protected by a passphrase, the server
          prompts the user for the passphrase. The password must be
          given interactively; it cannot be stored in a file. If the
          passphrase is incorrect, the program continues as if it could
          not read the key.
     </p>
     <p>
      This variable can be modified at runtime to affect the TLS
          context the server uses for new connections established after
          the execution of
      <a class="link" href="alter-instance.html#alter-instance-reload-tls">
       <code class="literal">
        ALTER INSTANCE RELOAD
          TLS
       </code>
      </a>
      or after a restart if the variable value was
          persisted. See
      <a class="xref" href="using-encrypted-connections.html#using-encrypted-connections-server-side-runtime-configuration" title="Server-Side Runtime Configuration and Monitoring for Encrypted Connections">
       Server-Side Runtime Configuration and Monitoring for Encrypted
        Connections
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ssl_session_cache_mode">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ssl_session_cache_mode">
       <code class="literal">
        ssl_session_cache_mode
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268744736">
     </a>
     <a class="indexterm" name="idm46045268743696">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ssl_session_cache_mode">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ssl_session_cache_mode={ON|OFF}
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ssl_session_cache_mode">
            ssl_session_cache_mode
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            ON
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            OFF
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Controls whether to enable the session cache in memory on the
          server side and session-ticket generation by the server. The
          default mode is
      <code class="literal">
       ON
      </code>
      (enable session cache
          mode). A change to the
      <a class="link" href="server-system-variables.html#sysvar_ssl_session_cache_mode">
       <code class="literal">
        ssl_session_cache_mode
       </code>
      </a>
      system
          variable has an effect only after the
      <a class="link" href="alter-instance.html#alter-instance-reload-tls">
       <code class="literal">
        ALTER INSTANCE RELOAD TLS
       </code>
      </a>
      statement has been executed, or after a restart if the
          variable value was persisted.
     </p>
     <p>
      These
      <a class="link" href="server-system-variables.html#sysvar_ssl_session_cache_mode">
       <code class="literal">
        ssl_session_cache_mode
       </code>
      </a>
      values are permitted:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          ON
         </code>
         : Enable session cache mode.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          OFF
         </code>
         : Disable session cache mode.
        </p>
       </li>
      </ul>
     </div>
     <p>
      The server does not advertise its support for session
          resumption if the value of this system variable is
      <code class="literal">
       OFF
      </code>
      . When running on OpenSSL
          1.0.
      <code class="literal">
       x
      </code>
      the session tickets are always
          generated, but the tickets are not usable when
      <a class="link" href="server-system-variables.html#sysvar_ssl_session_cache_mode">
       <code class="literal">
        ssl_session_cache_mode
       </code>
      </a>
      is
          enabled.
     </p>
     <p>
      The current value in effect for
      <a class="link" href="server-system-variables.html#sysvar_ssl_session_cache_mode">
       <code class="literal">
        ssl_session_cache_mode
       </code>
      </a>
      can be
          observed with the
      <a class="link" href="server-status-variables.html#statvar_Ssl_session_cache_mode">
       <code class="literal">
        Ssl_session_cache_mode
       </code>
      </a>
      status variable.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_ssl_session_cache_timeout">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_ssl_session_cache_timeout">
       <code class="literal">
        ssl_session_cache_timeout
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268700512">
     </a>
     <a class="indexterm" name="idm46045268699408">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for ssl_session_cache_timeout">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --ssl_session_cache_timeout
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_ssl_session_cache_timeout">
            ssl_session_cache_timeout
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           300
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           84600
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Sets a period of time during which prior session reuse is
          permitted when establishing a new encrypted connection to the
          server, provided the
      <a class="link" href="server-system-variables.html#sysvar_ssl_session_cache_mode">
       <code class="literal">
        ssl_session_cache_mode
       </code>
      </a>
      system
          variable is enabled and prior session data is available. If
          the session timeout expires, a session can no longer be
          reused.
     </p>
     <p>
      The default value is 300 seconds and the maximum value is
          84600 (or one day in seconds). A change to the
      <a class="link" href="server-system-variables.html#sysvar_ssl_session_cache_timeout">
       <code class="literal">
        ssl_session_cache_timeout
       </code>
      </a>
      system variable has an effect only after the
      <a class="link" href="alter-instance.html#alter-instance-reload-tls">
       <code class="literal">
        ALTER INSTANCE RELOAD TLS
       </code>
      </a>
      statement has been executed, or after a restart if the
          variable value was persisted. The current value in effect for
      <a class="link" href="server-system-variables.html#sysvar_ssl_session_cache_timeout">
       <code class="literal">
        ssl_session_cache_timeout
       </code>
      </a>
      can
          be observed with the
      <a class="link" href="server-status-variables.html#statvar_Ssl_session_cache_timeout">
       <code class="literal">
        Ssl_session_cache_timeout
       </code>
      </a>
      status variable.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_statement_id">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_statement_id">
       <code class="literal">
        statement_id
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268660528">
     </a>
     <a class="indexterm" name="idm46045268659440">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for statement_id">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_statement_id">
            statement_id
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Each statement executed in the current session is assigned a
          sequence number. This can be used together with the
      <a class="link" href="server-system-variables.html#sysvar_session_track_system_variables">
       <code class="literal">
        session_track_system_variables
       </code>
      </a>
      system variable to identify this statement in Performance
          Schema tables such as the
      <a class="link" href="performance-schema-events-statements-history-table.html" title="29.12.6.2 The events_statements_history Table">
       <code class="literal">
        events_statements_history
       </code>
      </a>
      table.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_stored_program_cache">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_stored_program_cache">
       <code class="literal">
        stored_program_cache
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268636800">
     </a>
     <a class="indexterm" name="idm46045268635760">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for stored_program_cache">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --stored-program-cache=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_stored_program_cache">
            stored_program_cache
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           256
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           16
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           524288
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Sets a soft upper limit for the number of cached stored
          routines per connection. The value of this variable is
          specified in terms of the number of stored routines held in
          each of the two caches maintained by the MySQL Server for,
          respectively, stored procedures and stored functions.
     </p>
     <p>
      Whenever a stored routine is executed this cache size is
          checked before the first or top-level statement in the routine
          is parsed; if the number of routines of the same type (stored
          procedures or stored functions according to which is being
          executed) exceeds the limit specified by this variable, the
          corresponding cache is flushed and memory previously allocated
          for cached objects is freed. This allows the cache to be
          flushed safely, even when there are dependencies between
          stored routines.
     </p>
     <p>
      The stored procedure and stored function caches exists in
          parallel with the stored program definition cache partition of
          the
      <a class="link" href="glossary.html#glos_dictionary_object_cache" title="dictionary object cache">
       dictionary
          object cache
      </a>
      . The stored procedure and stored function
          caches are per connection, while the stored program definition
          cache is shared. The existence of objects in the stored
          procedure and stored function caches have no dependence on the
          existence of objects in the stored program definition cache,
          and vice versa. For more information, see
      <a class="xref" href="data-dictionary-object-cache.html" title="16.4 Dictionary Object Cache">
       Section 16.4, “Dictionary Object Cache”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_stored_program_definition_cache">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_stored_program_definition_cache">
       <code class="literal">
        stored_program_definition_cache
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268602480">
     </a>
     <a class="indexterm" name="idm46045268601376">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for stored_program_definition_cache">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --stored-program-definition-cache=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_stored_program_definition_cache">
            stored_program_definition_cache
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           256
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           256
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           524288
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Defines a limit for the number of stored program definition
          objects, both used and unused, that can be kept in the
          dictionary object cache.
     </p>
     <p>
      Unused stored program definition objects are only kept in the
          dictionary object cache when the number in use is less than
          the capacity defined by
      <code class="literal">
       stored_program_definition_cache
      </code>
      .
     </p>
     <p>
      A setting of 0 means that stored program definition objects
          are only kept in the dictionary object cache while they are in
          use.
     </p>
     <p>
      The stored program definition cache partition exists in
          parallel with the stored procedure and stored function caches
          that are configured using the
      <a class="link" href="server-system-variables.html#sysvar_stored_program_cache">
       <code class="literal">
        stored_program_cache
       </code>
      </a>
      option.
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_stored_program_cache">
       <code class="literal">
        stored_program_cache
       </code>
      </a>
      option sets a soft upper limit for the number of cached stored
          procedures or functions per connection, and the limit is
          checked each time a connection executes a stored procedure or
          function. The stored program definition cache partition, on
          the other hand, is a shared cache that stores stored program
          definition objects for other purposes. The existence of
          objects in the stored program definition cache partition has
          no dependence on the existence of objects in the stored
          procedure cache or stored function cache, and vice versa.
     </p>
     <p>
      For related information, see
      <a class="xref" href="data-dictionary-object-cache.html" title="16.4 Dictionary Object Cache">
       Section 16.4, “Dictionary Object Cache”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_super_read_only">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_super_read_only">
       <code class="literal">
        super_read_only
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268563840">
     </a>
     <a class="indexterm" name="idm46045268562752">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for super_read_only">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --super-read-only[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_super_read_only">
            super_read_only
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If the
      <a class="link" href="server-system-variables.html#sysvar_read_only">
       <code class="literal">
        read_only
       </code>
      </a>
      system
          variable is enabled, the server permits no client updates
          except from users who have the
      <a class="link" href="privileges-provided.html#priv_connection-admin">
       <code class="literal">
        CONNECTION_ADMIN
       </code>
      </a>
      privilege (or
          the deprecated
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege). If the
      <a class="link" href="server-system-variables.html#sysvar_super_read_only">
       <code class="literal">
        super_read_only
       </code>
      </a>
      system
          variable is also enabled, the server prohibits client updates
          even from users who have
      <a class="link" href="privileges-provided.html#priv_connection-admin">
       <code class="literal">
        CONNECTION_ADMIN
       </code>
      </a>
      or
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      . See the description of
          the
      <a class="link" href="server-system-variables.html#sysvar_read_only">
       <code class="literal">
        read_only
       </code>
      </a>
      system variable
          for a description of read-only mode and information about how
      <a class="link" href="server-system-variables.html#sysvar_read_only">
       <code class="literal">
        read_only
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_super_read_only">
       <code class="literal">
        super_read_only
       </code>
      </a>
      interact.
     </p>
     <p>
      Client updates prevented when
      <a class="link" href="server-system-variables.html#sysvar_super_read_only">
       <code class="literal">
        super_read_only
       </code>
      </a>
      is enabled
          include operations that do not necessarily appear to be
          updates, such as
      <code class="literal">
       CREATE FUNCTION
      </code>
      (to
          install a loadable function),
      <code class="literal">
       INSTALL
          PLUGIN
      </code>
      , and
      <code class="literal">
       INSTALL COMPONENT
      </code>
      .
          These operations are prohibited because they involve changes
          to tables in the
      <code class="literal">
       mysql
      </code>
      system schema.
     </p>
     <p>
      Similarly, if the Event Scheduler is enabled, enabling the
      <a class="link" href="server-system-variables.html#sysvar_super_read_only">
       <code class="literal">
        super_read_only
       </code>
      </a>
      system
          variable prevents it from updating event
      <span class="quote">
       “
       <span class="quote">
        last
          executed
       </span>
       ”
      </span>
      timestamps in the
      <code class="literal">
       events
      </code>
      data dictionary table. This causes the Event Scheduler to stop
          the next time it tries to execute a scheduled event, after
          writing a message to the server error log. (In this situation
          the
      <a class="link" href="server-system-variables.html#sysvar_event_scheduler">
       <code class="literal">
        event_scheduler
       </code>
      </a>
      system
          variable does not change from
      <code class="literal">
       ON
      </code>
      to
      <code class="literal">
       OFF
      </code>
      . An implication is that this variable
          rejects the DBA
      <span class="emphasis">
       <em>
        intent
       </em>
      </span>
      that the Event
          Scheduler be enabled or disabled, where its actual status of
          started or stopped may be distinct.). If
      <a class="link" href="server-system-variables.html#sysvar_super_read_only">
       <code class="literal">
        super_read_only
       </code>
      </a>
      is
          subsequently disabled after being enabled, the server
          automatically restarts the Event Scheduler as needed.
     </p>
     <p>
      Changes to
      <a class="link" href="server-system-variables.html#sysvar_super_read_only">
       <code class="literal">
        super_read_only
       </code>
      </a>
      on
          a replication source server are not replicated to replica
          servers. The value can be set on a replica independent of the
          setting on the source.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_syseventlog.facility">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_syseventlog.facility">
       <code class="literal">
        syseventlog.facility
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268512432">
     </a>
     <a class="indexterm" name="idm46045268511392">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for syseventlog.facility">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --syseventlog.facility=value
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_syseventlog.facility">
            syseventlog.facility
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           daemon
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The facility for error log output written to
      <code class="literal">
       syslog
      </code>
      (what type of program is sending the
          message). This variable is unavailable unless the
      <code class="literal">
       log_sink_syseventlog
      </code>
      error log component is
          installed. See
      <a class="xref" href="error-log-syslog.html" title="7.4.2.8 Error Logging to the System Log">
       Section 7.4.2.8, “Error Logging to the System Log”
      </a>
      .
     </p>
     <p>
      The permitted values can vary per operating system; consult
          your system
      <code class="literal">
       syslog
      </code>
      documentation.
     </p>
     <p>
      This variable does not exist on Windows.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_syseventlog.include_pid">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_syseventlog.include_pid">
       <code class="literal">
        syseventlog.include_pid
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268482816">
     </a>
     <a class="indexterm" name="idm46045268481776">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for syseventlog.include_pid">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --syseventlog.include-pid[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_syseventlog.include_pid">
            syseventlog.include_pid
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether to include the server process ID in each line of error
          log output written to
      <code class="literal">
       syslog
      </code>
      . This variable
          is unavailable unless the
      <code class="literal">
       log_sink_syseventlog
      </code>
      error log component is
          installed. See
      <a class="xref" href="error-log-syslog.html" title="7.4.2.8 Error Logging to the System Log">
       Section 7.4.2.8, “Error Logging to the System Log”
      </a>
      .
     </p>
     <p>
      This variable does not exist on Windows.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_syseventlog.tag">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_syseventlog.tag">
       <code class="literal">
        syseventlog.tag
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268454640">
     </a>
     <a class="indexterm" name="idm46045268453552">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for syseventlog.tag">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --syseventlog.tag=tag
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_syseventlog.tag">
            syseventlog.tag
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           empty string
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The tag to be added to the server identifier in error log
          output written to
      <code class="literal">
       syslog
      </code>
      or the Windows
          Event Log. This variable is unavailable unless the
      <code class="literal">
       log_sink_syseventlog
      </code>
      error log component is
          installed. See
      <a class="xref" href="error-log-syslog.html" title="7.4.2.8 Error Logging to the System Log">
       Section 7.4.2.8, “Error Logging to the System Log”
      </a>
      .
     </p>
     <p>
      By default, no tag is set, so the server identifier is simply
      <code class="literal">
       MySQL
      </code>
      on Windows, and
      <code class="literal">
       mysqld
      </code>
      on other platforms. If a tag value
          of
      <em class="replaceable">
       <code>
        tag
       </code>
      </em>
      is specified, it is appended
          to the server identifier with a leading hyphen, resulting in a
      <code class="literal">
       syslog
      </code>
      identifier of
      <code class="literal">
       mysqld-
       <em class="replaceable">
        <code>
         tag
        </code>
       </em>
      </code>
      (or
      <code class="literal">
       MySQL-
       <em class="replaceable">
        <code>
         tag
        </code>
       </em>
      </code>
      on
          Windows).
     </p>
     <p>
      On Windows, to use a tag that does not already exist, the
          server must be run from an account with Administrator
          privileges, to permit creation of a registry entry for the
          tag. Elevated privileges are not required if the tag already
          exists.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_system_time_zone">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_system_time_zone">
       <code class="literal">
        system_time_zone
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268421008">
     </a>
     <a class="indexterm" name="idm46045268419920">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for system_time_zone">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_system_time_zone">
            system_time_zone
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The server system time zone. When the server begins executing,
          it inherits a time zone setting from the machine defaults,
          possibly modified by the environment of the account used for
          running the server or the startup script. The value is used to
          set
      <a class="link" href="server-system-variables.html#sysvar_system_time_zone">
       <code class="literal">
        system_time_zone
       </code>
      </a>
      . To
          explicitly specify the system time zone, set the
      <code class="literal">
       TZ
      </code>
      environment variable or use the
      <a class="link" href="mysqld-safe.html#option_mysqld_safe_timezone">
       <code class="option">
        --timezone
       </code>
      </a>
      option of the
      <a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
       <span class="command">
        <strong>
         mysqld_safe
        </strong>
       </span>
      </a>
      script.
     </p>
     <p>
      In addition to startup time initialization, if the server host
          time zone changes (for example, due to daylight saving time),
      <a class="link" href="server-system-variables.html#sysvar_system_time_zone">
       <code class="literal">
        system_time_zone
       </code>
      </a>
      reflects
          that change, which has these implications for applications:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         Queries that reference
         <a class="link" href="server-system-variables.html#sysvar_system_time_zone">
          <code class="literal">
           system_time_zone
          </code>
         </a>
         will get
              one value before a daylight saving change and a different
              value after the change.
        </p>
       </li>
       <li class="listitem">
        <p>
         For queries that begin executing before a daylight saving
              change and end after the change, the
         <a class="link" href="server-system-variables.html#sysvar_system_time_zone">
          <code class="literal">
           system_time_zone
          </code>
         </a>
         remains
              constant within the query because the value is usually
              cached at the beginning of execution.
        </p>
       </li>
      </ul>
     </div>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_system_time_zone">
       <code class="literal">
        system_time_zone
       </code>
      </a>
      variable
          differs from the
      <a class="link" href="server-system-variables.html#sysvar_time_zone">
       <code class="literal">
        time_zone
       </code>
      </a>
      variable. Although they might have the same value, the latter
          variable is used to initialize the time zone for each client
          that connects. See
      <a class="xref" href="time-zone-support.html" title="7.1.15 MySQL Server Time Zone Support">
       Section 7.1.15, “MySQL Server Time Zone Support”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_table_definition_cache">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_table_definition_cache">
       <code class="literal">
        table_definition_cache
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268385280">
     </a>
     <a class="indexterm" name="idm46045268384240">
     </a>
     <a class="indexterm" name="idm46045268382752">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for table_definition_cache">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --table-definition-cache=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_table_definition_cache">
            table_definition_cache
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           -1
          </code>
          (signifies autosizing; do not assign this literal value)
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           400
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           524288
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of table definitions that can be stored in the
          table definition cache. If you use a large number of tables,
          you can create a large table definition cache to speed up
          opening of tables. The table definition cache takes less space
          and does not use file descriptors, unlike the normal table
          cache. The minimum value is 400. The default value is based on
          the following formula, capped to a limit of 2000:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa13205830"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">MIN<span class="token punctuation">(</span>400 <span class="token operator">+</span> table_open_cache <span class="token operator">/</span> 2<span class="token punctuation">,</span> 2000<span class="token punctuation">)</span></code></pre>
     </div>
     <p>
      For
      <a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
       <code class="literal">
        InnoDB
       </code>
      </a>
      , the
      <a class="link" href="server-system-variables.html#sysvar_table_definition_cache">
       <code class="literal">
        table_definition_cache
       </code>
      </a>
      setting acts as a soft limit for the number of table instances
          in the dictionary object cache and the number file-per-table
          tablespaces that can be open at one time.
     </p>
     <p>
      If the number of table instances in the dictionary object
          cache exceeds the
      <a class="link" href="server-system-variables.html#sysvar_table_definition_cache">
       <code class="literal">
        table_definition_cache
       </code>
      </a>
      limit,
          an LRU mechanism begins marking table instances for eviction
          and eventually removes them from the dictionary object cache.
          The number of open tables with cached metadata can be higher
          than the
      <a class="link" href="server-system-variables.html#sysvar_table_definition_cache">
       <code class="literal">
        table_definition_cache
       </code>
      </a>
      limit
          due to table instances with foreign key relationships, which
          are not placed on the LRU list.
     </p>
     <p>
      The number of file-per-table tablespaces that can be open at
          one time is limited by both the
      <a class="link" href="server-system-variables.html#sysvar_table_definition_cache">
       <code class="literal">
        table_definition_cache
       </code>
      </a>
      and
      <a class="link" href="innodb-parameters.html#sysvar_innodb_open_files">
       <code class="literal">
        innodb_open_files
       </code>
      </a>
      settings.
          If both variables are set, the highest setting is used. If
          neither variable is set, the
      <a class="link" href="server-system-variables.html#sysvar_table_definition_cache">
       <code class="literal">
        table_definition_cache
       </code>
      </a>
      setting, which has a higher default value, is used. If the
          number of open tablespaces exceeds the limit defined by
      <a class="link" href="server-system-variables.html#sysvar_table_definition_cache">
       <code class="literal">
        table_definition_cache
       </code>
      </a>
      or
      <a class="link" href="innodb-parameters.html#sysvar_innodb_open_files">
       <code class="literal">
        innodb_open_files
       </code>
      </a>
      , an LRU
          mechanism searches the LRU list for tablespace files that are
          fully flushed and not currently being extended. This process
          is performed each time a new tablespace is opened. Only
          inactive tablespaces are closed.
     </p>
     <p>
      The table definition cache exists in parallel with the table
          definition cache partition of the
      <a class="link" href="glossary.html#glos_dictionary_object_cache" title="dictionary object cache">
       dictionary object
          cache
      </a>
      . Both caches store table definitions but serve
          different parts of the MySQL server. Objects in one cache have
          no dependence on the existence of objects in the other. For
          more information, see
      <a class="xref" href="data-dictionary-object-cache.html" title="16.4 Dictionary Object Cache">
       Section 16.4, “Dictionary Object Cache”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_table_encryption_privilege_check">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_table_encryption_privilege_check">
       <code class="literal">
        table_encryption_privilege_check
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268335536">
     </a>
     <a class="indexterm" name="idm46045268334432">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for table_encryption_privilege_check">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --table-encryption-privilege-check[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_table_encryption_privilege_check">
            table_encryption_privilege_check
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Controls the
      <a class="link" href="privileges-provided.html#priv_table-encryption-admin">
       <code class="literal">
        TABLE_ENCRYPTION_ADMIN
       </code>
      </a>
      privilege check that occurs when creating or altering a schema
          or general tablespace with encryption that differs from the
      <a class="link" href="server-system-variables.html#sysvar_default_table_encryption">
       <code class="literal">
        default_table_encryption
       </code>
      </a>
      setting, or when creating or altering a table with an
          encryption setting that differs from the default schema
          encryption. The check is disabled by default.
     </p>
     <p>
      Setting
      <a class="link" href="server-system-variables.html#sysvar_table_encryption_privilege_check">
       <code class="literal">
        table_encryption_privilege_check
       </code>
      </a>
      at runtime requires the
      <a class="link" href="privileges-provided.html#priv_super">
       <code class="literal">
        SUPER
       </code>
      </a>
      privilege.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_table_encryption_privilege_check">
       <code class="literal">
        table_encryption_privilege_check
       </code>
      </a>
      supports
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
          PERSIST
       </code>
      </a>
      and
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
          PERSIST_ONLY
       </code>
      </a>
      syntax. See
      <a class="xref" href="persisted-system-variables.html" title="7.1.9.3 Persisted System Variables">
       Section 7.1.9.3, “Persisted System Variables”
      </a>
      .
     </p>
     <p>
      For more information, see
      <a class="xref" href="innodb-data-encryption.html#innodb-schema-tablespace-encryption-default" title="Defining an Encryption Default for Schemas and General Tablespaces">
       Defining an Encryption Default for Schemas and General Tablespaces
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_table_open_cache">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_table_open_cache">
       <code class="literal">
        table_open_cache
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268297296">
     </a>
     <a class="indexterm" name="idm46045268296208">
     </a>
     <a class="indexterm" name="idm46045268294720">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for table_open_cache">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --table-open-cache=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_table_open_cache">
            table_open_cache
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           4000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           524288
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of open tables for all threads. Increasing this
          value increases the number of file descriptors that
      <a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
       <span class="command">
        <strong>
         mysqld
        </strong>
       </span>
      </a>
      requires. The effective value of
          this variable is the greater of the effective value of
      <a class="link" href="server-system-variables.html#sysvar_open_files_limit">
       <code class="literal">
        open_files_limit
       </code>
      </a>
      <code class="literal">
       -
          10 -
      </code>
      the effective value of
      <a class="link" href="server-system-variables.html#sysvar_max_connections">
       <code class="literal">
        max_connections
       </code>
      </a>
      <code class="literal">
       /
          2
      </code>
      , and 400; that is
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-simple"><div class="docs-select-all right" id="sa24169110"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">MAX<span class="token punctuation">(</span>
    <span class="token punctuation">(</span>open_files_limit <span class="token operator">-</span> 10 <span class="token operator">-</span> max_connections<span class="token punctuation">)</span> <span class="token operator">/</span> 2<span class="token punctuation">,</span>
    400
   <span class="token punctuation">)</span></code></pre>
     </div>
     <p>
      You can check whether you need to increase the table cache by
          checking the
      <a class="link" href="server-status-variables.html#statvar_Opened_tables">
       <code class="literal">
        Opened_tables
       </code>
      </a>
      status variable. If the value of
      <a class="link" href="server-status-variables.html#statvar_Opened_tables">
       <code class="literal">
        Opened_tables
       </code>
      </a>
      is large and
          you do not use
      <a class="link" href="flush.html#flush-tables">
       <code class="literal">
        FLUSH TABLES
       </code>
      </a>
      often (which just forces all tables to be closed and
          reopened), then you should increase the value of the
      <a class="link" href="server-system-variables.html#sysvar_table_open_cache">
       <code class="literal">
        table_open_cache
       </code>
      </a>
      variable.
          For more information about the table cache, see
      <a class="xref" href="table-cache.html" title="10.4.3.1 How MySQL Opens and Closes Tables">
       Section 10.4.3.1, “How MySQL Opens and Closes Tables”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_table_open_cache_instances">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_table_open_cache_instances">
       <code class="literal">
        table_open_cache_instances
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268252816">
     </a>
     <a class="indexterm" name="idm46045268251712">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for table_open_cache_instances">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --table-open-cache-instances=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_table_open_cache_instances">
            table_open_cache_instances
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           16
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           64
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of open tables cache instances. To improve
          scalability by reducing contention among sessions, the open
          tables cache can be partitioned into several smaller cache
          instances of size
      <a class="link" href="server-system-variables.html#sysvar_table_open_cache">
       <code class="literal">
        table_open_cache
       </code>
      </a>
      /
      <a class="link" href="server-system-variables.html#sysvar_table_open_cache_instances">
       <code class="literal">
        table_open_cache_instances
       </code>
      </a>
      .
          A session needs to lock only one instance to access it for DML
          statements. This segments cache access among instances,
          permitting higher performance for operations that use the
          cache when there are many sessions accessing tables. (DDL
          statements still require a lock on the entire cache, but such
          statements are much less frequent than DML statements.)
     </p>
     <p>
      A value of 8 or 16 is recommended on systems that routinely
          use 16 or more cores. However, if you have many large triggers
          on your tables that cause a high memory load, the default
          setting for
      <a class="link" href="server-system-variables.html#sysvar_table_open_cache_instances">
       <code class="literal">
        table_open_cache_instances
       </code>
      </a>
      might lead to excessive memory usage. In that situation, it
          can be helpful to set
      <a class="link" href="server-system-variables.html#sysvar_table_open_cache_instances">
       <code class="literal">
        table_open_cache_instances
       </code>
      </a>
      to
          1 in order to restrict memory usage.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_tablespace_definition_cache">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_tablespace_definition_cache">
       <code class="literal">
        tablespace_definition_cache
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268215808">
     </a>
     <a class="indexterm" name="idm46045268214704">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for tablespace_definition_cache">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --tablespace-definition-cache=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_tablespace_definition_cache">
            tablespace_definition_cache
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           256
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           256
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           524288
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Defines a limit for the number of tablespace definition
          objects, both used and unused, that can be kept in the
          dictionary object cache.
     </p>
     <p>
      Unused tablespace definition objects are only kept in the
          dictionary object cache when the number in use is less than
          the capacity defined by
      <code class="literal">
       tablespace_definition_cache
      </code>
      .
     </p>
     <p>
      A setting of
      <code class="literal">
       0
      </code>
      means that tablespace
          definition objects are only kept in the dictionary object
          cache while they are in use.
     </p>
     <p>
      For more information, see
      <a class="xref" href="data-dictionary-object-cache.html" title="16.4 Dictionary Object Cache">
       Section 16.4, “Dictionary Object Cache”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_temptable_max_mmap">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_temptable_max_mmap">
       <code class="literal">
        temptable_max_mmap
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268181360">
     </a>
     <a class="indexterm" name="idm46045268180320">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for temptable_max_mmap">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --temptable-max-mmap=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_temptable_max_mmap">
            temptable_max_mmap
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2^64-1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Defines the maximum amount of memory (in bytes) the TempTable
          storage engine is permitted to allocate from memory-mapped
          temporary files before it starts storing data to
      <code class="literal">
       InnoDB
      </code>
      internal temporary tables on disk. A
          setting of 0 (default) disables allocation of memory from
          memory-mapped temporary files. For more information, see
      <a class="xref" href="internal-temporary-tables.html" title="10.4.4 Internal Temporary Table Use in MySQL">
       Section 10.4.4, “Internal Temporary Table Use in MySQL”
      </a>
      .
     </p>
     <p>
      Before MySQL 8.4, this option was set to 1 GiB instead of 0.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_temptable_max_ram">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_temptable_max_ram">
       <code class="literal">
        temptable_max_ram
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268146608">
     </a>
     <a class="indexterm" name="idm46045268145568">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for temptable_max_ram">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --temptable-max-ram=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_temptable_max_ram">
            temptable_max_ram
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           3% of total memory: min 1 GB, max 4 GB
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           2097152
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2^64-1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Defines the maximum amount of memory that can be occupied by
          the
      <code class="literal">
       TempTable
      </code>
      storage engine before it
          starts storing data on disk. The default value is 3% of total
          memory available on the server, with a minimum and maximum
          default range of 1-4 GiB. For more information, see
      <a class="xref" href="internal-temporary-tables.html" title="10.4.4 Internal Temporary Table Use in MySQL">
       Section 10.4.4, “Internal Temporary Table Use in MySQL”
      </a>
      .
     </p>
     <p>
      Before MySQL 8.4, the default value was always 1 GiB.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_temptable_use_mmap">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_temptable_use_mmap">
       <code class="literal">
        temptable_use_mmap
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268111840">
     </a>
     <a class="indexterm" name="idm46045268110800">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for temptable_use_mmap">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --temptable-use-mmap[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_temptable_use_mmap">
            temptable_use_mmap
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Defines whether the TempTable storage engine allocates space
          for internal in-memory temporary tables as memory-mapped
          temporary files when the amount of memory occupied by the
          TempTable storage engine exceeds the limit defined by the
      <a class="link" href="server-system-variables.html#sysvar_temptable_max_ram">
       <code class="literal">
        temptable_max_ram
       </code>
      </a>
      variable.
          When
      <a class="link" href="server-system-variables.html#sysvar_temptable_use_mmap">
       <code class="literal">
        temptable_use_mmap
       </code>
      </a>
      is
          disabled (default), the TempTable storage engine uses
      <code class="literal">
       InnoDB
      </code>
      on-disk internal temporary tables
          instead. For more information, see
      <a class="xref" href="internal-temporary-tables.html" title="10.4.4 Internal Temporary Table Use in MySQL">
       Section 10.4.4, “Internal Temporary Table Use in MySQL”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_cache_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_cache_size">
       <code class="literal">
        thread_cache_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268079904">
     </a>
     <a class="indexterm" name="idm46045268078864">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_cache_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-cache-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_cache_size">
            thread_cache_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           -1
          </code>
          (signifies autosizing; do not assign this literal value)
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           16384
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      How many threads the server should cache for reuse. When a
          client disconnects, the client's threads are put in the cache
          if there are fewer than
      <a class="link" href="server-system-variables.html#sysvar_thread_cache_size">
       <code class="literal">
        thread_cache_size
       </code>
      </a>
      threads
          there. Requests for threads are satisfied by reusing threads
          taken from the cache if possible, and only when the cache is
          empty is a new thread created. This variable can be increased
          to improve performance if you have a lot of new connections.
          Normally, this does not provide a notable performance
          improvement if you have a good thread implementation. However,
          if your server sees hundreds of connections per second you
          should normally set
      <a class="link" href="server-system-variables.html#sysvar_thread_cache_size">
       <code class="literal">
        thread_cache_size
       </code>
      </a>
      high enough
          so that most new connections use cached threads. By examining
          the difference between the
      <a class="link" href="server-status-variables.html#statvar_Connections">
       <code class="literal">
        Connections
       </code>
      </a>
      and
      <a class="link" href="server-status-variables.html#statvar_Threads_created">
       <code class="literal">
        Threads_created
       </code>
      </a>
      status
          variables, you can see how efficient the thread cache is. For
          details, see
      <a class="xref" href="server-status-variables.html" title="7.1.10 Server Status Variables">
       Section 7.1.10, “Server Status Variables”
      </a>
      .
     </p>
     <p>
      The default value is based on the following formula, capped to
          a limit of 100:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa69513222"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">8 <span class="token operator">+</span> <span class="token punctuation">(</span>max_connections <span class="token operator">/</span> 100<span class="token punctuation">)</span></code></pre>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_handling">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_handling">
       <code class="literal">
        thread_handling
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268041376">
     </a>
     <a class="indexterm" name="idm46045268040288">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_handling">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-handling=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_handling">
            thread_handling
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           one-thread-per-connection
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            no-threads
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            one-thread-per-connection
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            loaded-dynamically
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The thread-handling model used by the server for connection
          threads. The permissible values are
      <code class="literal">
       no-threads
      </code>
      (the server uses a single thread
          to handle one connection),
      <code class="literal">
       one-thread-per-connection
      </code>
      (the server uses
          one thread to handle each client connection), and
      <code class="literal">
       loaded-dynamically
      </code>
      (set by the thread pool
          plugin when it initializes).
      <code class="literal">
       no-threads
      </code>
      is
          useful for debugging under Linux; see
      <a class="xref" href="debugging-mysql.html" title="7.9 Debugging MySQL">
       Section 7.9, “Debugging MySQL”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_algorithm">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_algorithm">
       <code class="literal">
        thread_pool_algorithm
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045268007024">
     </a>
     <a class="indexterm" name="idm46045268005984">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_algorithm">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-algorithm=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_algorithm">
            thread_pool_algorithm
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls which algorithm the thread pool plugin
          uses:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          0
         </code>
         : Use a conservative low-concurrency
              algorithm.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          1
         </code>
         : Use an aggressive high-currency
              algorithm which performs better with optimal thread
              counts, but performance may be degraded if the number of
              connections reaches extremely high values.
        </p>
       </li>
      </ul>
     </div>
     <p>
      This variable is available only if the thread pool plugin is
          enabled. See
      <a class="xref" href="thread-pool.html" title="7.6.3 MySQL Enterprise Thread Pool">
       Section 7.6.3, “MySQL Enterprise Thread Pool”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_dedicated_listeners">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_dedicated_listeners">
       <code class="literal">
        thread_pool_dedicated_listeners
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267971792">
     </a>
     <a class="indexterm" name="idm46045267970688">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_dedicated_listeners">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-dedicated-listeners
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_dedicated_listeners">
            thread_pool_dedicated_listeners
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Dedicates a listener thread in each thread group to listen for
          incoming statements from connections assigned to the group.
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          OFF
         </code>
         : (Default) Disables dedicated
              listener threads.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          ON
         </code>
         : Dedicates a listener thread in each
              thread group to listen for incoming statements from
              connections assigned to the group. Dedicated listener
              threads do not execute queries.
        </p>
       </li>
      </ul>
     </div>
     <p>
      Enabling
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_dedicated_listeners">
       <code class="literal">
        thread_pool_dedicated_listeners
       </code>
      </a>
      is only useful when a transaction limit is defined by
      <code class="literal">
       thread_pool_max_transactions_limit
      </code>
      .
          Otherwise,
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_dedicated_listeners">
       <code class="literal">
        thread_pool_dedicated_listeners
       </code>
      </a>
      should not be enabled.
     </p>
     <p>
      HeatWave Service uses this variable, which is available only with MySQL Enterprise Edition,
          and not supported in MySQL 8.4.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_high_priority_connection">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_high_priority_connection">
       <code class="literal">
        thread_pool_high_priority_connection
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267937936">
     </a>
     <a class="indexterm" name="idm46045267936896">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_high_priority_connection">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-high-priority-connection=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_high_priority_connection">
            thread_pool_high_priority_connection
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable affects queuing of new statements prior to
          execution. If the value is 0 (false, the default), statement
          queuing uses both the low-priority and high-priority queues.
          If the value is 1 (true), queued statements always go to the
          high-priority queue.
     </p>
     <p>
      This variable is available only if the thread pool plugin is
          enabled. See
      <a class="xref" href="thread-pool.html" title="7.6.3 MySQL Enterprise Thread Pool">
       Section 7.6.3, “MySQL Enterprise Thread Pool”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_longrun_trx_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_longrun_trx_limit">
       <code class="literal">
        thread_pool_longrun_trx_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267906032">
     </a>
     <a class="indexterm" name="idm46045267904928">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_longrun_trx_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-longrun-trx-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_longrun_trx_limit">
            thread_pool_longrun_trx_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           2000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           10
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           60*60*24
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          ms
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      When
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_max_transactions_limit">
       <code class="literal">
        thread_pool_max_transactions_limit
       </code>
      </a>
      is in use, there is a maximum number of transactions that can
          be active in each thread group. If entire number available is
          being used by long-running transactions, any additional
          transaction assigned to the group blocks until one of the
          long-running transactions is completed, which users can
          perceive as an inexplicable hang.
     </p>
     <p>
      To mitigate this issue, the limit for a given thread group is
          suspended if all of the threads using up the transaction
          maximum have been executing longer than the interval (in
          milliseconds) specified by
      <code class="literal">
       thread_pool_longrun_trx_limit
      </code>
      . When the
          number of long-running transactions decreases,
      <code class="literal">
       thread_pool_max_transactions_limit
      </code>
      can be
          (and is) enabled again. In order for this to happen, the
          number of ongoing transactions must be less than
      <code class="literal">
       thread_pool_max_transactions_limit / 2
      </code>
      for
          the interval defined as shown:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa97844416"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token function">MIN</span><span class="token punctuation">(</span> <span class="token function">MAX</span><span class="token punctuation">(</span>thread_pool_longrun_trx_limit <span class="token operator">*</span> <span class="token number">15</span><span class="token punctuation">,</span> <span class="token number">5000</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">30000</span><span class="token punctuation">)</span></code></pre>
     </div>
     <p>
      This variable is available only if the thread pool plugin is
          enabled. See
      <a class="xref" href="thread-pool.html" title="7.6.3 MySQL Enterprise Thread Pool">
       Section 7.6.3, “MySQL Enterprise Thread Pool”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_max_active_query_threads">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_max_active_query_threads">
       <code class="literal">
        thread_pool_max_active_query_threads
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267866384">
     </a>
     <a class="indexterm" name="idm46045267865344">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_max_active_query_threads">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-max-active-query-threads
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_max_active_query_threads">
            thread_pool_max_active_query_threads
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           512
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum permissible number of active (running) query
          threads per group. If the value is 0, the thread pool plugin
          uses up to as many threads as are available.
     </p>
     <p>
      This variable is available only if the thread pool plugin is
          enabled. See
      <a class="xref" href="thread-pool.html" title="7.6.3 MySQL Enterprise Thread Pool">
       Section 7.6.3, “MySQL Enterprise Thread Pool”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_max_transactions_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_max_transactions_limit">
       <code class="literal">
        thread_pool_max_transactions_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267834416">
     </a>
     <a class="indexterm" name="idm46045267833376">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_max_transactions_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-max-transactions-limit
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_max_transactions_limit">
            thread_pool_max_transactions_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           1000000
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum number of transactions permitted by the thread
          pool plugin. Defining a transaction limit binds a thread to a
          transaction until it commits, which helps stabilize throughput
          during high concurrency.
     </p>
     <p>
      The default value of 0 means that there is no transaction
          limit. The variable is dynamic but cannot be changed from 0 to
          a higher value at runtime and vice versa. A non-zero value at
          startup permits dynamic configuration at runtime. The
      <a class="link" href="privileges-provided.html#priv_connection-admin">
       <code class="literal">
        CONNECTION_ADMIN
       </code>
      </a>
      privilege is
          required to configure
      <code class="literal">
       thread_pool_max_transactions_limit
      </code>
      at
          runtime.
     </p>
     <p>
      When you define a transaction limit, enabling
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_dedicated_listeners">
       <code class="literal">
        thread_pool_dedicated_listeners
       </code>
      </a>
      creates a dedicated listener thread in each thread group. The
          additional dedicated listener thread consumes more resources
          and affects thread pool performance.
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_dedicated_listeners">
       <code class="literal">
        thread_pool_dedicated_listeners
       </code>
      </a>
      should therefore be used cautiously.
     </p>
     <p>
      When the limit defined by
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_max_transactions_limit">
       <code class="literal">
        thread_pool_max_transactions_limit
       </code>
      </a>
      has been reached, new connections or transactions on existing
          connections may appear to hang until one or more existing
          transactions are completed. It should be possible in many
          cases to mitigate this issue by setting
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_longrun_trx_limit">
       <code class="literal">
        thread_pool_longrun_trx_limit
       </code>
      </a>
      so that the transaction maximum can be relaxed when the number
          of ongoing transactions matches it for a given length of time.
          If existing connections continue to be blocked or long-running
          even after attempting this, a privileged connection may be
          required to access the server to increase the limit, remove
          the limit, or kill running transactions. See
      <a class="xref" href="thread-pool-operation.html#privileged-connections" title="Privileged Connections">
       Privileged Connections
      </a>
      .
     </p>
     <p>
      HeatWave Service uses this variable, which is available only with MySQL Enterprise Edition,
          and not supported in MySQL 8.4.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_max_unused_threads">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_max_unused_threads">
       <code class="literal">
        thread_pool_max_unused_threads
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267792560">
     </a>
     <a class="indexterm" name="idm46045267791456">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_max_unused_threads">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-max-unused-threads=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_max_unused_threads">
            thread_pool_max_unused_threads
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4096
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum permitted number of unused threads in the thread
          pool. This variable makes it possible to limit the amount of
          memory used by sleeping threads.
     </p>
     <p>
      A value of 0 (the default) means no limit on the number of
          sleeping threads. A value of
      <em class="replaceable">
       <code>
        N
       </code>
      </em>
      where
      <em class="replaceable">
       <code>
        N
       </code>
      </em>
      is greater than 0 means 1
          consumer thread and
      <em class="replaceable">
       <code>
        N
       </code>
      </em>
      −1
          reserve threads. In this case, if a thread is ready to sleep
          but the number of sleeping threads is already at the maximum,
          the thread exits rather than going to sleep.
     </p>
     <p>
      A sleeping thread is either sleeping as a consumer thread or a
          reserve thread. The thread pool permits one thread to be the
          consumer thread when sleeping. If a thread goes to sleep and
          there is no existing consumer thread, it sleeps as a consumer
          thread. When a thread must be woken up, a consumer thread is
          selected if there is one. A reserve thread is selected only
          when there is no consumer thread to wake up.
     </p>
     <p>
      This variable is available only if the thread pool plugin is
          enabled. See
      <a class="xref" href="thread-pool.html" title="7.6.3 MySQL Enterprise Thread Pool">
       Section 7.6.3, “MySQL Enterprise Thread Pool”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_prio_kickup_timer">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_prio_kickup_timer">
       <code class="literal">
        thread_pool_prio_kickup_timer
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267757072">
     </a>
     <a class="indexterm" name="idm46045267755968">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_prio_kickup_timer">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-prio-kickup-timer=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_prio_kickup_timer">
            thread_pool_prio_kickup_timer
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4294967294
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          milliseconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable affects statements waiting for execution in the
          low-priority queue. The value is the number of milliseconds
          before a waiting statement is moved to the high-priority
          queue. The default is 1000 (1 second).
     </p>
     <p>
      This variable is available only if the thread pool plugin is
          enabled. See
      <a class="xref" href="thread-pool.html" title="7.6.3 MySQL Enterprise Thread Pool">
       Section 7.6.3, “MySQL Enterprise Thread Pool”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_query_threads_per_group">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_query_threads_per_group">
       <code class="literal">
        thread_pool_query_threads_per_group
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267722960">
     </a>
     <a class="indexterm" name="idm46045267721920">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_query_threads_per_group">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-query-threads-per-group
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_query_threads_per_group">
            thread_pool_query_threads_per_group
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           4096
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The maximum number of query threads permitted in a thread
          group. The maximum value is 4096, but if
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_max_transactions_limit">
       <code class="literal">
        thread_pool_max_transactions_limit
       </code>
      </a>
      is set,
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_query_threads_per_group">
       <code class="literal">
        thread_pool_query_threads_per_group
       </code>
      </a>
      must not exceed that value.
     </p>
     <p>
      The default value of 1 means there is one active query thread
          in each thread group, which works well for many loads. When
          you are using the high concurrency thread pool algorithm
          (
      <code class="literal">
       thread_pool_algorithm = 1
      </code>
      ), consider
          increasing the value if you experience slower response times
          due to long-running transactions.
     </p>
     <p>
      The
      <a class="link" href="privileges-provided.html#priv_connection-admin">
       <code class="literal">
        CONNECTION_ADMIN
       </code>
      </a>
      privilege
          is required to configure
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_query_threads_per_group">
       <code class="literal">
        thread_pool_query_threads_per_group
       </code>
      </a>
      at runtime.
     </p>
     <p>
      If you decrease the value of
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_query_threads_per_group">
       <code class="literal">
        thread_pool_query_threads_per_group
       </code>
      </a>
      at runtime, threads that are currently running user queries
          are allowed to complete, then moved to the reserve pool or
          terminated. if you increment the value at runtime and the
          thread group needs more threads, these are taken from the
          reserve pool if possible, otherwise they are created.
     </p>
     <p>
      HeatWave Service uses this variable, which is available only with MySQL Enterprise Edition,
          and not supported in MySQL 8.4.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_size">
       <code class="literal">
        thread_pool_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267682656">
     </a>
     <a class="indexterm" name="idm46045267681568">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_size">
            thread_pool_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           16
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           512
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of thread groups in the thread pool. This is the
          most important parameter controlling thread pool performance.
          It affects how many statements can execute simultaneously. If
          a value outside the range of permissible values is specified,
          the thread pool plugin does not load and the server writes a
          message to the error log.
     </p>
     <p>
      This variable is available only if the thread pool plugin is
          enabled. See
      <a class="xref" href="thread-pool.html" title="7.6.3 MySQL Enterprise Thread Pool">
       Section 7.6.3, “MySQL Enterprise Thread Pool”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_stall_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_stall_limit">
       <code class="literal">
        thread_pool_stall_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267650336">
     </a>
     <a class="indexterm" name="idm46045267649296">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_stall_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-stall-limit=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_stall_limit">
            thread_pool_stall_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           6
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           4
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           600
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          milliseconds * 10
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable affects executing statements. The value is the
          amount of time a statement has to finish after starting to
          execute before it becomes defined as stalled, at which point
          the thread pool permits the thread group to begin executing
          another statement. The value is measured in 10 millisecond
          units, so the default of 6 means 60ms. Short wait values
          permit threads to start more quickly. Short values are also
          better for avoiding deadlock situations. Long wait values are
          useful for workloads that include long-running statements, to
          avoid starting too many new statements while the current ones
          execute.
     </p>
     <p>
      This variable is available only if the thread pool plugin is
          enabled. See
      <a class="xref" href="thread-pool.html" title="7.6.3 MySQL Enterprise Thread Pool">
       Section 7.6.3, “MySQL Enterprise Thread Pool”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_pool_transaction_delay">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_pool_transaction_delay">
       <code class="literal">
        thread_pool_transaction_delay
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267616016">
     </a>
     <a class="indexterm" name="idm46045267614912">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_pool_transaction_delay">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-pool-transaction-delay
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_pool_transaction_delay">
            thread_pool_transaction_delay
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           0
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           300000
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The delay period before executing a new transaction, in
          milliseconds. The maximum value is 300000 (5 minutes).
     </p>
     <p>
      A transaction delay can be used in cases where parallel
          transactions affect the performance of other operations due to
          resource contention. For example, if parallel transactions
          affect index creation or an online buffer pool resizing
          operation, you can configure a transaction delay to reduce
          resource contention while those operations are running.
     </p>
     <p>
      Worker threads sleep for the number of milliseconds specified
          by
      <code class="literal">
       thread_pool_transaction_delay
      </code>
      before
          executing a new transaction.
     </p>
     <p>
      The
      <code class="literal">
       thread_pool_transaction_delay
      </code>
      setting
          does not affect queries issued from a privileged connection (a
          connection assigned to the
      <code class="literal">
       Admin
      </code>
      thread
          group). These queries are not subject to a configured
          transaction delay.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_thread_stack">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_thread_stack">
       <code class="literal">
        thread_stack
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267581360">
     </a>
     <a class="indexterm" name="idm46045267580272">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for thread_stack">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --thread-stack=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_thread_stack">
            thread_stack
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1048576
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           131072
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (64-bit platforms)
         </th>
         <td>
          <code class="literal">
           18446744073709550592
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (32-bit platforms)
         </th>
         <td>
          <code class="literal">
           4294966272
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The stack size for each thread. The default is large enough
          for normal operation. If the thread stack size is too small,
          it limits the complexity of the SQL statements that the server
          can handle, the recursion depth of stored procedures, and
          other memory-consuming actions.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_time_zone">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_time_zone">
       <code class="literal">
        time_zone
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267543104">
     </a>
     <a class="indexterm" name="idm46045267542016">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for time_zone">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_time_zone">
            time_zone
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           SYSTEM
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           -13:59
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           +14:00
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The current time zone. This variable is used to initialize the
          time zone for each client that connects. By default, the
          initial value of this is
      <code class="literal">
       'SYSTEM'
      </code>
      (which
          means,
      <span class="quote">
       “
       <span class="quote">
        use the value of
        <a class="link" href="server-system-variables.html#sysvar_system_time_zone">
         <code class="literal">
          system_time_zone
         </code>
        </a>
       </span>
       ”
      </span>
      ).
          The value can be specified explicitly at server startup with
          the
      <a class="link" href="server-options.html#option_mysqld_default-time-zone">
       <code class="option">
        --default-time-zone
       </code>
      </a>
      option.
          See
      <a class="xref" href="time-zone-support.html" title="7.1.15 MySQL Server Time Zone Support">
       Section 7.1.15, “MySQL Server Time Zone Support”
      </a>
      .
     </p>
     <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Note
      </div>
      <p>
       If set to
       <code class="literal">
        SYSTEM
       </code>
       , every MySQL function
            call that requires a time zone calculation makes a system
            library call to determine the current system time zone. This
            call may be protected by a global mutex, resulting in
            contention.
      </p>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_timestamp">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_timestamp">
       <code class="literal">
        timestamp
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267509248">
     </a>
     <a class="indexterm" name="idm46045267508160">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for timestamp">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_timestamp">
            timestamp
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Numeric
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           UNIX_TIMESTAMP()
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           2147483647
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Set the time for this client. This is used to get the original
          timestamp if you use the binary log to restore rows.
      <em class="replaceable">
       <code>
        timestamp_value
       </code>
      </em>
      should be a Unix
          epoch timestamp (a value like that returned by
      <a class="link" href="date-and-time-functions.html#function_unix-timestamp">
       <code class="literal">
        UNIX_TIMESTAMP()
       </code>
      </a>
      , not a value
          in
      <code class="literal">
       '
       <em class="replaceable">
        <code>
         YYYY-MM-DD
          hh:mm:ss
        </code>
       </em>
       '
      </code>
      format) or
      <code class="literal">
       DEFAULT
      </code>
      .
     </p>
     <p>
      Setting
      <a class="link" href="server-system-variables.html#sysvar_timestamp">
       <code class="literal">
        timestamp
       </code>
      </a>
      to a
          constant value causes it to retain that value until it is
          changed again. Setting
      <a class="link" href="server-system-variables.html#sysvar_timestamp">
       <code class="literal">
        timestamp
       </code>
      </a>
      to
      <code class="literal">
       DEFAULT
      </code>
      causes its value to be the current
          date and time as of the time it is accessed.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_timestamp">
       <code class="literal">
        timestamp
       </code>
      </a>
      is a
      <code class="literal">
       DOUBLE
      </code>
      rather than
      <code class="literal">
       BIGINT
      </code>
      because its value includes a
          microseconds part. The maximum value corresponds to
      <code class="literal">
       '2038-01-19 03:14:07'
      </code>
      UTC, the same as for
          the
      <a class="link" href="datetime.html" title="13.2.2 The DATE, DATETIME, and TIMESTAMP Types">
       <code class="literal">
        TIMESTAMP
       </code>
      </a>
      data type.
     </p>
     <p>
      <code class="literal">
       SET timestamp
      </code>
      affects the value returned by
      <a class="link" href="date-and-time-functions.html#function_now">
       <code class="literal">
        NOW()
       </code>
      </a>
      but not by
      <a class="link" href="date-and-time-functions.html#function_sysdate">
       <code class="literal">
        SYSDATE()
       </code>
      </a>
      . This means that
          timestamp settings in the binary log have no effect on
          invocations of
      <a class="link" href="date-and-time-functions.html#function_sysdate">
       <code class="literal">
        SYSDATE()
       </code>
      </a>
      . The
          server can be started with the
      <a class="link" href="server-options.html#option_mysqld_sysdate-is-now">
       <code class="option">
        --sysdate-is-now
       </code>
      </a>
      option to
          cause
      <a class="link" href="date-and-time-functions.html#function_sysdate">
       <code class="literal">
        SYSDATE()
       </code>
      </a>
      to be a synonym
          for
      <a class="link" href="date-and-time-functions.html#function_now">
       <code class="literal">
        NOW()
       </code>
      </a>
      , in which case
      <code class="literal">
       SET timestamp
      </code>
      affects both functions.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_tls_certificates_enforced_validation">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_tls_certificates_enforced_validation">
       <code class="literal">
        tls_certificates_enforced_validation
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267459104">
     </a>
     <a class="indexterm" name="idm46045267458016">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for tls_certificates_enforced_validation">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --tls-certificates-enforced-validation[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_tls_certificates_enforced_validation">
            tls_certificates_enforced_validation
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      During startup, the server ensures that the location of each
          required SSL certificate file is present in the default data
          directory if the file locations are not given on the command
          line. However, the server does not validate the certificate
          files and, as a result, it is able to start with an invalid
          certificate. The
      <a class="link" href="server-system-variables.html#sysvar_tls_certificates_enforced_validation">
       <code class="literal">
        tls_certificates_enforced_validation
       </code>
      </a>
      system variable controls whether certificate validation is
          enforced at startup. Discovery of an invalid certificate halts
          the startup execution when validation enforcement is enabled.
          By default, certificate validation enforcement is disabled
          (
      <code class="literal">
       OFF
      </code>
      ).
     </p>
     <p>
      Validation enforcement can be enabled by specifying the
      <code class="option">
       --tls-certificates-enforced-validation
      </code>
      option
          on the command line with or without the
      <code class="literal">
       ON
      </code>
      value. With validation enforcement enabled, certificates are
          also validated at the time of reloading them through the
      <a class="link" href="alter-instance.html#alter-instance-reload-tls">
       <code class="literal">
        ALTER INSTANCE RELOAD TLS
       </code>
      </a>
      statement. This system variable cannot be persisted across
          reboots. For more information, see
      <a class="xref" href="using-encrypted-connections.html#enforce-certificate-validation" title="Configuring Certificate Validation Enforcement">
       Configuring Certificate Validation Enforcement
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_tls_ciphersuites">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_tls_ciphersuites">
       <code class="literal">
        tls_ciphersuites
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267426992">
     </a>
     <a class="indexterm" name="idm46045267425904">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for tls_ciphersuites">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --tls-ciphersuites=ciphersuite_list
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_tls_ciphersuites">
            tls_ciphersuites
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           NULL
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Which ciphersuites the server permits for encrypted
          connections that use TLSv1.3. The value is a list of zero or
          more colon-separated ciphersuite names from among those listed
          here:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          TLS_AES_128_GCM_SHA256
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          TLS_AES_256_GCM_SHA384
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          TLS_CHACHA20_POLY1305_SHA256
         </code>
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          TLS_AES_128_CCM_SHA256
         </code>
        </p>
       </li>
      </ul>
     </div>
     <p>
      Trying to include any values in the cipher list that are not
          shown here when setting this variable raises an error
          (
      <a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_blocked_cipher" target="_top">
       <code class="literal">
        ER_BLOCKED_CIPHER
       </code>
      </a>
      ).
     </p>
     <p>
      The ciphersuites that can be named for this variable depend on
          the SSL library used to compile MySQL. If this variable is not
          set, its default value is
      <code class="literal">
       NULL
      </code>
      , which means
          that the server permits the default set of ciphersuites. If
          the variable is set to the empty string, no ciphersuites are
          enabled and encrypted connections cannot be established. For
          more information, see
      <a class="xref" href="encrypted-connection-protocols-ciphers.html" title="8.3.2 Encrypted Connection TLS Protocols and Ciphers">
       Section 8.3.2, “Encrypted Connection TLS Protocols and Ciphers”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_tls_version">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_tls_version">
       <code class="literal">
        tls_version
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267391088">
     </a>
     <a class="indexterm" name="idm46045267390000">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for tls_version">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --tls-version=protocol_list
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_tls_version">
            tls_version
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           TLSv1.2,TLSv1.3
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Which protocols the server permits for encrypted connections.
          The value is a list of one or more comma-separated protocol
          names, which are not case-sensitive. The protocols that can be
          named for this variable depend on the SSL library used to
          compile MySQL. Permitted protocols should be chosen such as
          not to leave
      <span class="quote">
       “
       <span class="quote">
        holes
       </span>
       ”
      </span>
      in the list. For details,
          see
      <a class="xref" href="encrypted-connection-protocols-ciphers.html" title="8.3.2 Encrypted Connection TLS Protocols and Ciphers">
       Section 8.3.2, “Encrypted Connection TLS Protocols and Ciphers”
      </a>
      .
     </p>
     <p>
      This variable can be modified at runtime to affect the TLS
          context the server uses for new connections. See
      <a class="xref" href="using-encrypted-connections.html#using-encrypted-connections-server-side-runtime-configuration" title="Server-Side Runtime Configuration and Monitoring for Encrypted Connections">
       Server-Side Runtime Configuration and Monitoring for Encrypted
        Connections
      </a>
      .
     </p>
     <div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
      <div class="admon-title">
       Important
      </div>
      <div class="itemizedlist">
       <ul class="itemizedlist" style="list-style-type: circle; ">
        <li class="listitem">
         <p>
          MySQL 8.4 does not support the TLSv1 and
                TLSv1.1 connection protocols. See
          <a class="xref" href="encrypted-connection-protocols-ciphers.html#encrypted-connection-deprecated-protocols" title="Removal of Support for the TLSv1 and TLSv1.1 Protocols">
           Removal of Support for the TLSv1 and TLSv1.1 Protocols
          </a>
          for more information.
         </p>
        </li>
        <li class="listitem">
         <p>
          Support for the TLSv1.3 protocol is available in MySQL
                8.4, provided that MySQL Server was
                compiled using OpenSSL 1.1.1 or higher. The server
                checks the version of OpenSSL at startup, and if it is
                lower than 1.1.1, TLSv1.3 is removed from the default
                value for the system variable. In that case, the default
                is
          <code class="literal">
           TLSv1.2
          </code>
          .
         </p>
        </li>
       </ul>
      </div>
     </div>
     <p>
      Setting this variable to an empty string disables encrypted
          connections.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_tmp_table_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_tmp_table_size">
       <code class="literal">
        tmp_table_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267357792">
     </a>
     <a class="indexterm" name="idm46045267356704">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for tmp_table_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --tmp-table-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_tmp_table_size">
            tmp_table_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           16777216
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           18446744073709551615
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Defines the maximum size of internal in-memory temporary
          tables created by the
      <code class="literal">
       MEMORY
      </code>
      and
      <code class="literal">
       TempTable
      </code>
      storage engines. If an internal
          in-memory temporary table exceeds this size, it is
          automatically converted to an on-disk internal temporary
          table.
     </p>
     <p>
      The
      <a class="link" href="server-system-variables.html#sysvar_tmp_table_size">
       <code class="literal">
        tmp_table_size
       </code>
      </a>
      variable
          does not apply to user-created
      <code class="literal">
       MEMORY
      </code>
      tables. User-created
      <code class="literal">
       TempTable
      </code>
      tables are
          not supported.
     </p>
     <p>
      When using the
      <code class="literal">
       MEMORY
      </code>
      storage engine for
          internal in-memory temporary tables, the actual size limit is
          the smaller of
      <a class="link" href="server-system-variables.html#sysvar_tmp_table_size">
       <code class="literal">
        tmp_table_size
       </code>
      </a>
      and
      <a class="link" href="server-system-variables.html#sysvar_max_heap_table_size">
       <code class="literal">
        max_heap_table_size
       </code>
      </a>
      . The
      <a class="link" href="server-system-variables.html#sysvar_max_heap_table_size">
       <code class="literal">
        max_heap_table_size
       </code>
      </a>
      setting
          does not apply to
      <code class="literal">
       TempTable
      </code>
      tables.
     </p>
     <p>
      Increase the value of
      <a class="link" href="server-system-variables.html#sysvar_tmp_table_size">
       <code class="literal">
        tmp_table_size
       </code>
      </a>
      (and
      <a class="link" href="server-system-variables.html#sysvar_max_heap_table_size">
       <code class="literal">
        max_heap_table_size
       </code>
      </a>
      if
          necessary when using the
      <code class="literal">
       MEMORY
      </code>
      storage
          engine for internal in-memory temporary tables) if you do many
          advanced
      <code class="literal">
       GROUP BY
      </code>
      queries and you have lots
          of memory.
     </p>
     <p>
      You can compare the number of internal on-disk temporary
          tables created to the total number of internal temporary
          tables created by comparing
      <a class="link" href="server-status-variables.html#statvar_Created_tmp_disk_tables">
       <code class="literal">
        Created_tmp_disk_tables
       </code>
      </a>
      and
      <a class="link" href="server-status-variables.html#statvar_Created_tmp_tables">
       <code class="literal">
        Created_tmp_tables
       </code>
      </a>
      values.
     </p>
     <p>
      See also
      <a class="xref" href="internal-temporary-tables.html" title="10.4.4 Internal Temporary Table Use in MySQL">
       Section 10.4.4, “Internal Temporary Table Use in MySQL”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_tmpdir">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_tmpdir">
       <code class="literal">
        tmpdir
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267306112">
     </a>
     <a class="indexterm" name="idm46045267305040">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for tmpdir">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --tmpdir=dir_name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_tmpdir">
            tmpdir
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Directory name
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The path of the directory to use for creating temporary files.
          It might be useful if your default
      <code class="literal">
       /tmp
      </code>
      directory resides on a partition that is too small to hold
          temporary tables. This variable can be set to a list of
          several paths that are used in round-robin fashion. Paths
          should be separated by colon characters (
      <code class="literal">
       :
      </code>
      )
          on Unix and semicolon characters (
      <code class="literal">
       ;
      </code>
      ) on
          Windows.
     </p>
     <p>
      <a class="link" href="server-system-variables.html#sysvar_tmpdir">
       <code class="literal">
        tmpdir
       </code>
      </a>
      can be a non-permanent
          location, such as a directory on a memory-based file system or
          a directory that is cleared when the server host restarts. If
          the MySQL server is acting as a replica, and you are using a
          non-permanent location for
      <a class="link" href="server-system-variables.html#sysvar_tmpdir">
       <code class="literal">
        tmpdir
       </code>
      </a>
      , consider setting a
          different temporary directory for the replica using the
      <a class="link" href="replication-options-replica.html#sysvar_replica_load_tmpdir">
       <code class="literal">
        replica_load_tmpdir
       </code>
      </a>
      variable.
          For a replica, the temporary files used to replicate
      <a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
       <code class="literal">
        LOAD DATA
       </code>
      </a>
      statements are stored
          in this directory, so with a permanent location they can
          survive machine restarts, although replication can now
          continue after a restart if the temporary files have been
          removed.
     </p>
     <p>
      For more information about the storage location of temporary
          files, see
      <a class="xref" href="temporary-files.html" title="B.3.3.5 Where MySQL Stores Temporary Files">
       Section B.3.3.5, “Where MySQL Stores Temporary Files”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_transaction_alloc_block_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_transaction_alloc_block_size">
       <code class="literal">
        transaction_alloc_block_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267273408">
     </a>
     <a class="indexterm" name="idm46045267272304">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for transaction_alloc_block_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --transaction-alloc-block-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_transaction_alloc_block_size">
            transaction_alloc_block_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           8192
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           131072
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The amount in bytes by which to increase a per-transaction
          memory pool which needs memory. See the description of
      <a class="link" href="server-system-variables.html#sysvar_transaction_prealloc_size">
       <code class="literal">
        transaction_prealloc_size
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_transaction_isolation">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_transaction_isolation">
       <code class="literal">
        transaction_isolation
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267236384">
     </a>
     <a class="indexterm" name="idm46045267235344">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for transaction-isolation">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --transaction-isolation=name
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_transaction_isolation">
            transaction_isolation
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           REPEATABLE-READ
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            READ-UNCOMMITTED
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            READ-COMMITTED
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            REPEATABLE-READ
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            SERIALIZABLE
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The transaction isolation level. The default is
      <a class="link" href="innodb-transaction-isolation-levels.html#isolevel_repeatable-read">
       <code class="literal">
        REPEATABLE-READ
       </code>
      </a>
      .
     </p>
     <p>
      The transaction isolation level has three scopes: global,
          session, and next transaction. This three-scope implementation
          leads to some nonstandard isolation-level assignment
          semantics, as described later.
     </p>
     <p>
      To set the global transaction isolation level at startup, use
          the
      <a class="link" href="server-options.html#option_mysqld_transaction-isolation">
       <code class="option">
        --transaction-isolation
       </code>
      </a>
      server option.
     </p>
     <p>
      At runtime, the isolation level can be set directly using the
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
       </code>
      </a>
      statement to assign a value to the
      <a class="link" href="server-system-variables.html#sysvar_transaction_isolation">
       <code class="literal">
        transaction_isolation
       </code>
      </a>
      system
          variable, or indirectly using the
      <a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
       <code class="literal">
        SET
          TRANSACTION
       </code>
      </a>
      statement. If you set
      <a class="link" href="server-system-variables.html#sysvar_transaction_isolation">
       <code class="literal">
        transaction_isolation
       </code>
      </a>
      directly to an isolation level name that contains a space, the
          name should be enclosed within quotation marks, with the space
          replaced by a dash. For example, use this
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
       </code>
      </a>
      statement to set the global value:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa98593769"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> transaction_isolation <span class="token operator">=</span> <span class="token string">'READ-COMMITTED'</span><span class="token punctuation">;</span></code></pre>
     </div>
     <p>
      Setting the global
      <a class="link" href="server-system-variables.html#sysvar_transaction_isolation">
       <code class="literal">
        transaction_isolation
       </code>
      </a>
      value
          sets the isolation level for all subsequent sessions. Existing
          sessions are unaffected.
     </p>
     <p>
      To set the session or next-level
      <a class="link" href="server-system-variables.html#sysvar_transaction_isolation">
       <code class="literal">
        transaction_isolation
       </code>
      </a>
      value,
          use the
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
       </code>
      </a>
      statement. For most session system variables, these statements
          are equivalent ways to set the value:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa7868422"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@@SESSION.<em class="replaceable">var_name</em></span> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">SESSION</span> <em class="replaceable">var_name</em> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <em class="replaceable">var_name</em> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token variable">@@<em class="replaceable">var_name</em></span> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span></code></pre>
     </div>
     <p>
      As mentioned previously, the transaction isolation level has a
          next-transaction scope, in addition to the global and session
          scopes. To enable the next-transaction scope to be set,
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
       </code>
      </a>
      syntax for assigning session system variable values has
          nonstandard semantics for
      <a class="link" href="server-system-variables.html#sysvar_transaction_isolation">
       <code class="literal">
        transaction_isolation
       </code>
      </a>
      :
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         To set the session isolation level, use any of these
              syntaxes:
        </p>
        <div class="copytoclipboard-wrapper">
         <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa9668898"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@@SESSION.transaction_isolation</span> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">SESSION</span> transaction_isolation <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> transaction_isolation <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span></code></pre>
        </div>
        <p>
         For each of those syntaxes, these semantics apply:
        </p>
        <div class="itemizedlist">
         <ul class="itemizedlist" style="list-style-type: square; ">
          <li class="listitem">
           <p>
            Sets the isolation level for all subsequent
                  transactions performed within the session.
           </p>
          </li>
          <li class="listitem">
           <p>
            Permitted within transactions, but does not affect the
                  current ongoing transaction.
           </p>
          </li>
          <li class="listitem">
           <p>
            If executed between transactions, overrides any
                  preceding statement that sets the next-transaction
                  isolation level.
           </p>
          </li>
          <li class="listitem">
           <p>
            Corresponds to
            <a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
             <code class="literal">
              SET
                  SESSION TRANSACTION ISOLATION LEVEL
             </code>
            </a>
            (with
                  the
            <code class="literal">
             SESSION
            </code>
            keyword).
           </p>
          </li>
         </ul>
        </div>
       </li>
       <li class="listitem">
        <p>
         To set the next-transaction isolation level, use this
              syntax:
        </p>
        <div class="copytoclipboard-wrapper">
         <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa30157045"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@@transaction_isolation</span> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span></code></pre>
        </div>
        <p>
         For that syntax, these semantics apply:
        </p>
        <div class="itemizedlist">
         <ul class="itemizedlist" style="list-style-type: square; ">
          <li class="listitem">
           <p>
            Sets the isolation level only for the next single
                  transaction performed within the session.
           </p>
          </li>
          <li class="listitem">
           <p>
            Subsequent transactions revert to the session
                  isolation level.
           </p>
          </li>
          <li class="listitem">
           <p>
            Not permitted within transactions.
           </p>
          </li>
          <li class="listitem">
           <p>
            Corresponds to
            <a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
             <code class="literal">
              SET
                  TRANSACTION ISOLATION LEVEL
             </code>
            </a>
            (without the
            <code class="literal">
             SESSION
            </code>
            keyword).
           </p>
          </li>
         </ul>
        </div>
       </li>
      </ul>
     </div>
     <p>
      For more information about
      <a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
       <code class="literal">
        SET
          TRANSACTION
       </code>
      </a>
      and its relationship to the
      <a class="link" href="server-system-variables.html#sysvar_transaction_isolation">
       <code class="literal">
        transaction_isolation
       </code>
      </a>
      system
          variable, see
      <a class="xref" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
       Section 15.3.7, “SET TRANSACTION Statement”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_transaction_prealloc_size">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_transaction_prealloc_size">
       <code class="literal">
        transaction_prealloc_size
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267158944">
     </a>
     <a class="indexterm" name="idm46045267157840">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for transaction_prealloc_size">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --transaction-prealloc-size=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Deprecated
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_transaction_prealloc_size">
            transaction_prealloc_size
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           4096
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value
         </th>
         <td>
          <code class="literal">
           131072
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          bytes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
           Block Size
          </a>
         </th>
         <td>
          <code class="literal">
           1024
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      There is a per-transaction memory pool from which various
          transaction-related allocations take memory. The initial size
          of the pool in bytes is
      <code class="literal">
       transaction_prealloc_size
      </code>
      . For every
          allocation that cannot be satisfied from the pool because it
          has insufficient memory available, the pool is increased by
      <a class="link" href="server-system-variables.html#sysvar_transaction_alloc_block_size">
       <code class="literal">
        transaction_alloc_block_size
       </code>
      </a>
      bytes. When the transaction ends, the pool is truncated to
      <code class="literal">
       transaction_prealloc_size
      </code>
      bytes. By making
      <code class="literal">
       transaction_prealloc_size
      </code>
      sufficiently
          large to contain all statements within a single transaction,
          you can avoid many
      <code class="literal">
       malloc()
      </code>
      calls.
     </p>
     <p>
      <code class="literal">
       transaction_prealloc_size
      </code>
      is deprecated,
          and setting this variable no longer has any effect. Expect
      <code class="literal">
       transaction_prealloc_size
      </code>
      to be removed in
          a future release of MySQL.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_transaction_read_only">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
       <code class="literal">
        transaction_read_only
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267113824">
     </a>
     <a class="indexterm" name="idm46045267112784">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for transaction-read-only">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --transaction-read-only[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
            transaction_read_only
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           OFF
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The transaction access mode. The value can be
      <code class="literal">
       OFF
      </code>
      (read/write; the default) or
      <code class="literal">
       ON
      </code>
      (read only).
     </p>
     <p>
      The transaction access mode has three scopes: global, session,
          and next transaction. This three-scope implementation leads to
          some nonstandard access-mode assignment semantics, as
          described later.
     </p>
     <p>
      To set the global transaction access mode at startup, use the
      <a class="link" href="server-options.html#option_mysqld_transaction-read-only">
       <code class="option">
        --transaction-read-only
       </code>
      </a>
      server
          option.
     </p>
     <p>
      At runtime, the access mode can be set directly using the
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
       </code>
      </a>
      statement to assign a value to the
      <a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
       <code class="literal">
        transaction_read_only
       </code>
      </a>
      system
          variable, or indirectly using the
      <a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
       <code class="literal">
        SET
          TRANSACTION
       </code>
      </a>
      statement. For example, use this
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
       </code>
      </a>
      statement to set the global value:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa79528805"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> transaction_read_only <span class="token operator">=</span> <span class="token keyword">ON</span><span class="token punctuation">;</span></code></pre>
     </div>
     <p>
      Setting the global
      <a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
       <code class="literal">
        transaction_read_only
       </code>
      </a>
      value
          sets the access mode for all subsequent sessions. Existing
          sessions are unaffected.
     </p>
     <p>
      To set the session or next-level
      <a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
       <code class="literal">
        transaction_read_only
       </code>
      </a>
      value,
          use the
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
       </code>
      </a>
      statement. For most session system variables, these statements
          are equivalent ways to set the value:
     </p>
     <div class="copytoclipboard-wrapper">
      <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16273460"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@@SESSION.<em class="replaceable">var_name</em></span> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">SESSION</span> <em class="replaceable">var_name</em> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <em class="replaceable">var_name</em> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token variable">@@<em class="replaceable">var_name</em></span> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span></code></pre>
     </div>
     <p>
      As mentioned previously, the transaction access mode has a
          next-transaction scope, in addition to the global and session
          scopes. To enable the next-transaction scope to be set,
      <a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
       <code class="literal">
        SET
       </code>
      </a>
      syntax for assigning session system variable values has
          nonstandard semantics for
      <a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
       <code class="literal">
        transaction_read_only
       </code>
      </a>
      ,
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         To set the session access mode, use any of these syntaxes:
        </p>
        <div class="copytoclipboard-wrapper">
         <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa71468346"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@@SESSION.transaction_read_only</span> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">SESSION</span> transaction_read_only <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> transaction_read_only <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span></code></pre>
        </div>
        <p>
         For each of those syntaxes, these semantics apply:
        </p>
        <div class="itemizedlist">
         <ul class="itemizedlist" style="list-style-type: square; ">
          <li class="listitem">
           <p>
            Sets the access mode for all subsequent transactions
                  performed within the session.
           </p>
          </li>
          <li class="listitem">
           <p>
            Permitted within transactions, but does not affect the
                  current ongoing transaction.
           </p>
          </li>
          <li class="listitem">
           <p>
            If executed between transactions, overrides any
                  preceding statement that sets the next-transaction
                  access mode.
           </p>
          </li>
          <li class="listitem">
           <p>
            Corresponds to
            <a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
             <code class="literal">
              SET
                  SESSION TRANSACTION {READ WRITE | READ ONLY}
             </code>
            </a>
            (with the
            <code class="literal">
             SESSION
            </code>
            keyword).
           </p>
          </li>
         </ul>
        </div>
       </li>
       <li class="listitem">
        <p>
         To set the next-transaction access mode, use this syntax:
        </p>
        <div class="copytoclipboard-wrapper">
         <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa97939771"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@@transaction_read_only</span> <span class="token operator">=</span> <span class="token keyword"><em class="replaceable">value</em></span><span class="token punctuation">;</span></code></pre>
        </div>
        <p>
         For that syntax, these semantics apply:
        </p>
        <div class="itemizedlist">
         <ul class="itemizedlist" style="list-style-type: square; ">
          <li class="listitem">
           <p>
            Sets the access mode only for the next single
                  transaction performed within the session.
           </p>
          </li>
          <li class="listitem">
           <p>
            Subsequent transactions revert to the session access
                  mode.
           </p>
          </li>
          <li class="listitem">
           <p>
            Not permitted within transactions.
           </p>
          </li>
          <li class="listitem">
           <p>
            Corresponds to
            <a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
             <code class="literal">
              SET
                  TRANSACTION {READ WRITE | READ ONLY}
             </code>
            </a>
            (without the
            <code class="literal">
             SESSION
            </code>
            keyword).
           </p>
          </li>
         </ul>
        </div>
       </li>
      </ul>
     </div>
     <p>
      For more information about
      <a class="link" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
       <code class="literal">
        SET
          TRANSACTION
       </code>
      </a>
      and its relationship to the
      <a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
       <code class="literal">
        transaction_read_only
       </code>
      </a>
      system
          variable, see
      <a class="xref" href="set-transaction.html" title="15.3.7 SET TRANSACTION Statement">
       Section 15.3.7, “SET TRANSACTION Statement”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_unique_checks">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_unique_checks">
       <code class="literal">
        unique_checks
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267043552">
     </a>
     <a class="indexterm" name="idm46045267042464">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for unique_checks">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_unique_checks">
            unique_checks
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      If set to 1 (the default), uniqueness checks for secondary
          indexes in
      <code class="literal">
       InnoDB
      </code>
      tables are performed. If
          set to 0, storage engines are permitted to assume that
          duplicate keys are not present in input data. If you know for
          certain that your data does not contain uniqueness violations,
          you can set this to 0 to speed up large table imports to
      <code class="literal">
       InnoDB
      </code>
      .
     </p>
     <p>
      Setting this variable to 0 does not
      <span class="emphasis">
       <em>
        require
       </em>
      </span>
      storage engines to ignore
          duplicate keys. An engine is still permitted to check for them
          and issue duplicate-key errors if it detects them.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_updatable_views_with_limit">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_updatable_views_with_limit">
       <code class="literal">
        updatable_views_with_limit
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045267017536">
     </a>
     <a class="indexterm" name="idm46045267016432">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for updatable_views_with_limit">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --updatable-views-with-limit[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_updatable_views_with_limit">
            updatable_views_with_limit
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      This variable controls whether updates to a view can be made
          when the view does not contain all columns of the primary key
          defined in the underlying table, if the update statement
          contains a
      <code class="literal">
       LIMIT
      </code>
      clause. (Such updates
          often are generated by GUI tools.) An update is an
      <a class="link" href="update.html" title="15.2.17 UPDATE Statement">
       <code class="literal">
        UPDATE
       </code>
      </a>
      or
      <a class="link" href="delete.html" title="15.2.2 DELETE Statement">
       <code class="literal">
        DELETE
       </code>
      </a>
      statement. Primary key
          here means a
      <code class="literal">
       PRIMARY KEY
      </code>
      , or a
      <code class="literal">
       UNIQUE
      </code>
      index in which no column can contain
      <code class="literal">
       NULL
      </code>
      .
     </p>
     <p>
      The variable can have two values:
     </p>
     <div class="itemizedlist">
      <ul class="itemizedlist" style="list-style-type: circle; ">
       <li class="listitem">
        <p>
         <code class="literal">
          1
         </code>
         or
         <code class="literal">
          YES
         </code>
         : Issue a
              warning only (not an error message). This is the default
              value.
        </p>
       </li>
       <li class="listitem">
        <p>
         <code class="literal">
          0
         </code>
         or
         <code class="literal">
          NO
         </code>
         : Prohibit
              the update.
        </p>
       </li>
      </ul>
     </div>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_use_secondary_engine">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_use_secondary_engine">
       <code class="literal">
        use_secondary_engine
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045266980928">
     </a>
     <a class="indexterm" name="idm46045266979888">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for use_secondary_engine">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_use_secondary_engine">
            use_secondary_engine
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Enumeration
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Valid Values
         </th>
         <td>
          <p class="valid-value">
           <code class="literal">
            OFF
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            ON
           </code>
          </p>
          <p class="valid-value">
           <code class="literal">
            FORCED
           </code>
          </p>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      For future use.
     </p>
     <p>
      Whether to execute queries using a secondary engine.
     </p>
     <p>
      For use with HeatWave. See
      <a class="ulink" href="/doc/heatwave/en/" target="_top">
       HeatWave User Guide
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       validate_password.
       <em class="replaceable">
        <code>
         xxx
        </code>
       </em>
      </code>
     </p>
     <p>
      The
      <code class="literal">
       validate_password
      </code>
      component implements
          a set of system variables having names of the form
      <code class="literal">
       validate_password.
       <em class="replaceable">
        <code>
         xxx
        </code>
       </em>
      </code>
      .
          These variables affect password testing by that component; see
      <a class="xref" href="validate-password-options-variables.html" title="8.4.3.2 Password Validation Options and Variables">
       Section 8.4.3.2, “Password Validation Options and Variables”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_version">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_version">
       <code class="literal">
        version
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045266946752">
     </a>
     <a class="indexterm" name="idm46045266945680">
     </a>
     <p>
      The version number for the server. The value might also
          include a suffix indicating server build or configuration
          information.
      <code class="option">
       -debug
      </code>
      indicates that the server
          was built with debugging support enabled.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_version_comment">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_version_comment">
       <code class="literal">
        version_comment
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045266940784">
     </a>
     <a class="indexterm" name="idm46045266939696">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for version_comment">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_version_comment">
            version_comment
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The
      <span class="command">
       <strong>
        CMake
       </strong>
      </span>
      configuration program has a
      <a class="link" href="source-configuration-options.html#option_cmake_compilation_comment_server">
       <code class="option">
        COMPILATION_COMMENT_SERVER
       </code>
      </a>
      option that permits a comment to be specified when building
          MySQL. This variable contains the value of that comment.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_version_compile_machine">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_version_compile_machine">
       <code class="literal">
        version_compile_machine
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045266918176">
     </a>
     <a class="indexterm" name="idm46045266917136">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for version_compile_machine">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_version_compile_machine">
            version_compile_machine
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The type of the server binary.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_version_compile_os">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_version_compile_os">
       <code class="literal">
        version_compile_os
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045266897424">
     </a>
     <a class="indexterm" name="idm46045266896384">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for version_compile_os">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_version_compile_os">
            version_compile_os
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The type of operating system on which MySQL was built.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_version_compile_zlib">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_version_compile_zlib">
       <code class="literal">
        version_compile_zlib
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045266876704">
     </a>
     <a class="indexterm" name="idm46045266875664">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for version_compile_zlib">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_version_compile_zlib">
            version_compile_zlib
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          String
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The version of the compiled-in
      <code class="literal">
       zlib
      </code>
      library.
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_wait_timeout">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_wait_timeout">
       <code class="literal">
        wait_timeout
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045266855392">
     </a>
     <a class="indexterm" name="idm46045266854304">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for wait_timeout">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --wait-timeout=#
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_wait_timeout">
            wait_timeout
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Integer
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           28800
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Minimum Value
         </th>
         <td>
          <code class="literal">
           1
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Windows)
         </th>
         <td>
          <code class="literal">
           2147483
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Maximum Value (Other)
         </th>
         <td>
          <code class="literal">
           31536000
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Unit
         </th>
         <td>
          seconds
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      The number of seconds the server waits for activity on a
          noninteractive connection before closing it.
     </p>
     <p>
      On thread startup, the session
      <a class="link" href="server-system-variables.html#sysvar_wait_timeout">
       <code class="literal">
        wait_timeout
       </code>
      </a>
      value is
          initialized from the global
      <a class="link" href="server-system-variables.html#sysvar_wait_timeout">
       <code class="literal">
        wait_timeout
       </code>
      </a>
      value or from
          the global
      <a class="link" href="server-system-variables.html#sysvar_interactive_timeout">
       <code class="literal">
        interactive_timeout
       </code>
      </a>
      value,
          depending on the type of client (as defined by the
      <code class="literal">
       CLIENT_INTERACTIVE
      </code>
      connect option to
      <a class="ulink" href="/doc/c-api/8.4/en/mysql-real-connect.html" target="_top">
       <code class="literal">
        mysql_real_connect()
       </code>
      </a>
      ). See
          also
      <a class="link" href="server-system-variables.html#sysvar_interactive_timeout">
       <code class="literal">
        interactive_timeout
       </code>
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_warning_count">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_warning_count">
       <code class="literal">
        warning_count
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045266812912">
     </a>
     <a class="indexterm" name="idm46045266811824">
     </a>
     <p>
      The number of errors, warnings, and notes that resulted from
          the last statement that generated messages. This variable is
          read only. See
      <a class="xref" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
       Section 15.7.7.42, “SHOW WARNINGS Statement”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_windowing_use_high_precision">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_windowing_use_high_precision">
       <code class="literal">
        windowing_use_high_precision
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045266806672">
     </a>
     <a class="indexterm" name="idm46045266805568">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for windowing_use_high_precision">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --windowing-use-high-precision[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_windowing_use_high_precision">
            windowing_use_high_precision
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      Whether to compute window operations without loss of
          precision. See
      <a class="xref" href="window-function-optimization.html" title="10.2.1.21 Window Function Optimization">
       Section 10.2.1.21, “Window Function Optimization”
      </a>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <a name="sysvar_xa_detach_on_prepare">
      </a>
      <a class="link" href="server-system-variables.html#sysvar_xa_detach_on_prepare">
       <code class="literal">
        xa_detach_on_prepare
       </code>
      </a>
     </p>
     <a class="indexterm" name="idm46045266779984">
     </a>
     <a class="indexterm" name="idm46045266778944">
     </a>
     <div class="informaltable">
      <table frame="box" rules="all" summary="Properties for xa_detach_on_prepare">
       <colgroup>
        <col style="width: 30%"/>
        <col style="width: 70%"/>
       </colgroup>
       <tbody>
        <tr>
         <th>
          Command-Line Format
         </th>
         <td>
          <code class="literal">
           --xa-detach-on-prepare[={OFF|ON}]
          </code>
         </td>
        </tr>
        <tr>
         <th>
          System Variable
         </th>
         <td>
          <code class="literal">
           <a class="link" href="server-system-variables.html#sysvar_xa_detach_on_prepare">
            xa_detach_on_prepare
           </a>
          </code>
         </td>
        </tr>
        <tr>
         <th>
          Scope
         </th>
         <td>
          Global, Session
         </td>
        </tr>
        <tr>
         <th>
          Dynamic
         </th>
         <td>
          Yes
         </td>
        </tr>
        <tr>
         <th>
          <a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
           <code class="literal">
            SET_VAR
           </code>
          </a>
          Hint Applies
         </th>
         <td>
          No
         </td>
        </tr>
        <tr>
         <th>
          Type
         </th>
         <td>
          Boolean
         </td>
        </tr>
        <tr>
         <th>
          Default Value
         </th>
         <td>
          <code class="literal">
           ON
          </code>
         </td>
        </tr>
       </tbody>
      </table>
     </div>
     <p>
      When set to
      <code class="literal">
       ON
      </code>
      (enabled), all XA
          transactions are detached (disconnected) from the connection
          (session) as part of
      <a class="link" href="xa-statements.html" title="15.3.8.1 XA Transaction SQL Statements">
       <code class="literal">
        XA
          PREPARE
       </code>
      </a>
      . This means that the XA transaction can be
          committed or rolled back by another connection, even if the
          originating connection has not terminated, and this connection
          can start new transactions.
     </p>
     <p>
      Temporary tables cannot be used inside detached XA
          transactions.
     </p>
     <p>
      When this is
      <code class="literal">
       OFF
      </code>
      (disabled), an XA
          transaction is strictly associated with the same connection
          until the session disconnects. It is recommended that you
          allow it to be enabled (the default behavior) for replication.
     </p>
     <p>
      For more information, see
      <a class="xref" href="xa-states.html" title="15.3.8.2 XA Transaction States">
       Section 15.3.8.2, “XA Transaction States”
      </a>
      .
     </p>
    </li>
   </ul>
  </div>
 </div>
 <br/>
</div>
