<div id="docs-body">
 <div class="section">
  <div class="titlepage">
   <div>
    <div>
     <h4 class="title">
      <a name="sys-sys-config">
      </a>
      30.4.2.1 The sys_config Table
     </h4>
    </div>
   </div>
  </div>
  <a class="indexterm" name="idm46045063503696">
  </a>
  <a class="indexterm" name="idm46045063502208">
  </a>
  <p>
   This table contains
   <a class="link" href="sys-schema.html" title="Chapter 30 MySQL sys Schema">
    <code class="literal">
     sys
    </code>
   </a>
   schema
          configuration options, one row per option. Configuration
          changes made by updating this table persist across client
          sessions and server restarts.
  </p>
  <p>
   The
   <a class="link" href="sys-sys-config.html" title="30.4.2.1 The sys_config Table">
    <code class="literal">
     sys_config
    </code>
   </a>
   table has these
          columns:
  </p>
  <div class="itemizedlist">
   <ul class="itemizedlist" style="list-style-type: disc; ">
    <li class="listitem">
     <p>
      <code class="literal">
       variable
      </code>
     </p>
     <p>
      The configuration option name.
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       value
      </code>
     </p>
     <p>
      The configuration option value.
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       set_time
      </code>
     </p>
     <p>
      The timestamp of the most recent modification to the row.
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       set_by
      </code>
     </p>
     <p>
      The account that made the most recent modification to the
              row. The value is
      <code class="literal">
       NULL
      </code>
      if the row has
              not been changed since the
      <a class="link" href="sys-schema.html" title="Chapter 30 MySQL sys Schema">
       <code class="literal">
        sys
       </code>
      </a>
      schema was installed.
     </p>
    </li>
   </ul>
  </div>
  <p>
   As an efficiency measure to minimize the number of direct
          reads from the
   <a class="link" href="sys-sys-config.html" title="30.4.2.1 The sys_config Table">
    <code class="literal">
     sys_config
    </code>
   </a>
   table,
   <a class="link" href="sys-schema.html" title="Chapter 30 MySQL sys Schema">
    <code class="literal">
     sys
    </code>
   </a>
   schema functions that use a
          value from this table check for a user-defined variable with a
          corresponding name, which is the user-defined variable having
          the same name plus a
   <code class="literal">
    @sys.
   </code>
   prefix. (For
          example, the variable corresponding to the
   <code class="literal">
    diagnostics.include_raw
   </code>
   option is
   <code class="literal">
    @sys.diagnostics.include_raw
   </code>
   .) If the
          user-defined variable exists in the current session and is
          non-
   <code class="literal">
    NULL
   </code>
   , the function uses its value in
          preference to the value in the
   <a class="link" href="sys-sys-config.html" title="30.4.2.1 The sys_config Table">
    <code class="literal">
     sys_config
    </code>
   </a>
   table. Otherwise, the
          function reads and uses the value from the table. In the
          latter case, the calling function conventionally also sets the
          corresponding user-defined variable to the table value so that
          further references to the configuration option within the same
          session use the variable and need not read the table again.
  </p>
  <p>
   For example, the
   <code class="literal">
    statement_truncate_len
   </code>
   option controls the maximum length of statements returned by
          the
   <a class="link" href="sys-format-statement.html" title="30.4.5.5 The format_statement() Function">
    <code class="literal">
     format_statement()
    </code>
   </a>
   function.
          The default is 64. To temporarily change the value to 32 for
          your current session, set the corresponding
   <code class="literal">
    @sys.statement_truncate_len
   </code>
   user-defined
          variable:
  </p>
  <div class="copytoclipboard-wrapper">
   <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa59966965"><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">@stmt</span> <span class="token operator">=</span> <span class="token string">'SELECT variable, value, set_time, set_by FROM sys_config'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql&gt;</span> <span class="token keyword">SELECT</span> sys<span class="token punctuation">.</span>format_statement<span class="token punctuation">(</span><span class="token variable">@stmt</span><span class="token punctuation">)</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 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><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>
<span class="token output"><span class="token punctuation">|</span> sys.format_statement(@stmt)                              <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 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><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>
<span class="token output"><span class="token punctuation">|</span> SELECT variable, value, set_time, set_by FROM sys_config <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 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><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>
<span class="token prompt">mysql&gt;</span> <span class="token keyword">SET</span> <span class="token variable">@sys.statement_truncate_len</span> <span class="token operator">=</span> <span class="token number">32</span><span class="token punctuation">;</span>
<span class="token prompt">mysql&gt;</span> <span class="token keyword">SELECT</span> sys<span class="token punctuation">.</span>format_statement<span class="token punctuation">(</span><span class="token variable">@stmt</span><span class="token punctuation">)</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 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>
<span class="token output"><span class="token punctuation">|</span> sys.format_statement(@stmt)       <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 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>
<span class="token output"><span class="token punctuation">|</span> SELECT variabl ... ROM sys_config <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 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></code></pre>
  </div>
  <p>
   Subsequent invocations of
   <a class="link" href="sys-format-statement.html" title="30.4.5.5 The format_statement() Function">
    <code class="literal">
     format_statement()
    </code>
   </a>
   within the
          session continue to use the user-defined variable value (32),
          rather than the value stored in the table (64).
  </p>
  <p>
   To stop using the user-defined variable and revert to using
          the value in the table, set the variable to
   <code class="literal">
    NULL
   </code>
   within your session:
  </p>
  <div class="copytoclipboard-wrapper">
   <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa4167757"><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">@sys.statement_truncate_len</span> <span class="token operator">=</span> <span class="token boolean">NULL</span><span class="token punctuation">;</span>
<span class="token prompt">mysql&gt;</span> <span class="token keyword">SELECT</span> sys<span class="token punctuation">.</span>format_statement<span class="token punctuation">(</span><span class="token variable">@stmt</span><span class="token punctuation">)</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 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><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>
<span class="token output"><span class="token punctuation">|</span> sys.format_statement(@stmt)                              <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 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><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>
<span class="token output"><span class="token punctuation">|</span> SELECT variable, value, set_time, set_by FROM sys_config <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 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><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></code></pre>
  </div>
  <p>
   Alternatively, end your current session (causing the
          user-defined variable to no longer exist) and begin a new
          session.
  </p>
  <p>
   The conventional relationship just described between options
          in the
   <a class="link" href="sys-sys-config.html" title="30.4.2.1 The sys_config Table">
    <code class="literal">
     sys_config
    </code>
   </a>
   table and
          user-defined variables can be exploited to make temporary
          configuration changes that end when your session ends.
          However, if you set a user-defined variable and then
          subsequently change the corresponding table value within the
          same session, the changed table value is not used in that
          session as long as the user-defined variable exists with a
          non-
   <code class="literal">
    NULL
   </code>
   value. (The changed table value
   <span class="emphasis">
    <em>
     is
    </em>
   </span>
   used in other sessions in which the
          user-defined variable is not assigned.)
  </p>
  <p>
   The following list describes the options in the
   <a class="link" href="sys-sys-config.html" title="30.4.2.1 The sys_config Table">
    <code class="literal">
     sys_config
    </code>
   </a>
   table and the
          corresponding user-defined variables:
  </p>
  <div class="itemizedlist">
   <ul class="itemizedlist" style="list-style-type: disc; ">
    <li class="listitem">
     <p>
      <code class="literal">
       diagnostics.allow_i_s_tables
      </code>
      ,
      <code class="literal">
       @sys.diagnostics.allow_i_s_tables
      </code>
     </p>
     <p>
      If this option is
      <code class="literal">
       ON
      </code>
      , the
      <a class="link" href="sys-diagnostics.html" title="30.4.4.2 The diagnostics() Procedure">
       <code class="literal">
        diagnostics()
       </code>
      </a>
      procedure is
              permitted to perform table scans on the Information Schema
      <a class="link" href="information-schema-tables-table.html" title="28.3.38 The INFORMATION_SCHEMA TABLES Table">
       <code class="literal">
        TABLES
       </code>
      </a>
      table. This can be
              expensive if there are many tables. The default is
      <code class="literal">
       OFF
      </code>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       diagnostics.include_raw
      </code>
      ,
      <code class="literal">
       @sys.diagnostics.include_raw
      </code>
     </p>
     <p>
      If this option is
      <code class="literal">
       ON
      </code>
      , the
      <a class="link" href="sys-diagnostics.html" title="30.4.4.2 The diagnostics() Procedure">
       <code class="literal">
        diagnostics()
       </code>
      </a>
      procedure
              includes the raw output from querying the
      <a class="link" href="sys-metrics.html" title="30.4.3.21 The metrics View">
       <code class="literal">
        metrics
       </code>
      </a>
      view. The default is
      <code class="literal">
       OFF
      </code>
      .
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       ps_thread_trx_info.max_length
      </code>
      ,
      <code class="literal">
       @sys.ps_thread_trx_info.max_length
      </code>
     </p>
     <p>
      The maximum length for JSON output produced by the
      <a class="link" href="sys-ps-thread-trx-info.html" title="30.4.5.17 The ps_thread_trx_info() Function">
       <code class="literal">
        ps_thread_trx_info()
       </code>
      </a>
      function. The default is 65535.
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       statement_performance_analyzer.limit
      </code>
      ,
      <code class="literal">
       @sys.statement_performance_analyzer.limit
      </code>
     </p>
     <p>
      The maximum number of rows to return for views that have
              no built-in limit. (For example, the
      <a class="link" href="sys-statements-with-runtimes-in-95th-percentile.html" title="30.4.3.38 The statements_with_runtimes_in_95th_percentile and x$statements_with_runtimes_in_95th_percentile Views">
       <code class="literal">
        statements_with_runtimes_in_95th_percentile
       </code>
      </a>
      view has a built-in limit in the sense that it returns
              only statements with average execution time in the 95th
              percentile.) The default is 100.
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       statement_performance_analyzer.view
      </code>
      ,
      <code class="literal">
       @sys.statement_performance_analyzer.view
      </code>
     </p>
     <p>
      The custom query or view to be used by the
      <a class="link" href="sys-statement-performance-analyzer.html" title="30.4.4.25 The statement_performance_analyzer() Procedure">
       <code class="literal">
        statement_performance_analyzer()
       </code>
      </a>
      procedure (which is itself invoked by the
      <a class="link" href="sys-diagnostics.html" title="30.4.4.2 The diagnostics() Procedure">
       <code class="literal">
        diagnostics()
       </code>
      </a>
      procedure). If
              the option value contains a space, it is interpreted as a
              query. Otherwise, it must be the name of an existing view
              that queries the Performance Schema
      <a class="link" href="performance-schema-statement-summary-tables.html" title="29.12.20.3 Statement Summary Tables">
       <code class="literal">
        events_statements_summary_by_digest
       </code>
      </a>
      table. There cannot be any
      <code class="literal">
       LIMIT
      </code>
      clause
              in the query or view definition if the
      <code class="literal">
       statement_performance_analyzer.limit
      </code>
      configuration option is greater than 0. The default is
      <code class="literal">
       NULL
      </code>
      (no custom view defined).
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       statement_truncate_len
      </code>
      ,
      <code class="literal">
       @sys.statement_truncate_len
      </code>
     </p>
     <p>
      The maximum length of statements returned by the
      <a class="link" href="sys-format-statement.html" title="30.4.5.5 The format_statement() Function">
       <code class="literal">
        format_statement()
       </code>
      </a>
      function.
              Longer statements are truncated to this length. The
              default is 64.
     </p>
    </li>
   </ul>
  </div>
  <p>
   Other options can be added to the
   <a class="link" href="sys-sys-config.html" title="30.4.2.1 The sys_config Table">
    <code class="literal">
     sys_config
    </code>
   </a>
   table. For example,
          the
   <a class="link" href="sys-diagnostics.html" title="30.4.4.2 The diagnostics() Procedure">
    <code class="literal">
     diagnostics()
    </code>
   </a>
   and
   <a class="link" href="sys-execute-prepared-stmt.html" title="30.4.4.3 The execute_prepared_stmt() Procedure">
    <code class="literal">
     execute_prepared_stmt()
    </code>
   </a>
   procedures use the
   <code class="literal">
    debug
   </code>
   option if it
          exists, but this option is not part of the
   <a class="link" href="sys-sys-config.html" title="30.4.2.1 The sys_config Table">
    <code class="literal">
     sys_config
    </code>
   </a>
   table by default
          because debug output normally is enabled only temporarily, by
          setting the corresponding
   <code class="literal">
    @sys.debug
   </code>
   user-defined variable. To enable debug output without having
          to set that variable in individual sessions, add the option to
          the table:
  </p>
  <div class="copytoclipboard-wrapper">
   <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa59684147"><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">INSERT</span> <span class="token keyword">INTO</span> sys<span class="token punctuation">.</span>sys_config <span class="token punctuation">(</span>variable<span class="token punctuation">,</span> <span class="token keyword">value</span><span class="token punctuation">)</span> <span class="token keyword">VALUES</span><span class="token punctuation">(</span><span class="token string">'debug'</span><span class="token punctuation">,</span> <span class="token string">'ON'</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
  </div>
  <p>
   To change the debug setting in the table, do two things.
          First, modify the value in the table itself:
  </p>
  <div class="copytoclipboard-wrapper">
   <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa73381260"><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">UPDATE</span> sys<span class="token punctuation">.</span>sys_config
       <span class="token keyword">SET</span> <span class="token keyword">value</span> <span class="token operator">=</span> <span class="token string">'OFF'</span>
       <span class="token keyword">WHERE</span> variable <span class="token operator">=</span> <span class="token string">'debug'</span><span class="token punctuation">;</span></code></pre>
  </div>
  <p>
   Second, to also ensure that procedure invocations within the
          current session use the changed value from the table, set the
          corresponding user-defined variable to
   <code class="literal">
    NULL
   </code>
   :
  </p>
  <div class="copytoclipboard-wrapper">
   <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa13522173"><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">@sys.debug</span> <span class="token operator">=</span> <span class="token boolean">NULL</span><span class="token punctuation">;</span></code></pre>
  </div>
 </div>
 <br/>
</div>
