<div id="docs-body">
 <div class="section">
  <div class="titlepage">
   <div>
    <div>
     <h3 class="title">
      <a name="group-replication-network-partitioning">
      </a>
      20.7.8 Handling a Network Partition and Loss of Quorum
     </h3>
    </div>
   </div>
  </div>
  <a class="indexterm" name="idm46045131888752">
  </a>
  <p>
   The group needs to achieve consensus whenever a change that needs
      to be replicated happens. This is the case for regular
      transactions but is also required for group membership changes and
      some internal messaging that keeps the group consistent. Consensus
      requires a majority of group members to agree on a given decision.
      When a majority of group members is lost, the group is unable to
      progress and blocks because it cannot secure majority or quorum.
  </p>
  <p>
   Quorum may be lost when there are multiple involuntary failures,
      causing a majority of servers to be removed abruptly from the
      group. For example, in a group of 5 servers, if 3 of them become
      silent at once, the majority is compromised and thus no quorum can
      be achieved. In fact, the remaining two are not able to tell if
      the other 3 servers have crashed or whether a network partition
      has isolated these 2 alone and therefore the group cannot be
      reconfigured automatically.
  </p>
  <p>
   On the other hand, if servers exit the group voluntarily, they
      instruct the group that it should reconfigure itself. In practice,
      this means that a server that is leaving tells others that it is
      going away. This means that other members can reconfigure the
      group properly, the consistency of the membership is maintained
      and the majority is recalculated. For example, in the above
      scenario of 5 servers where 3 leave at once, if the 3 leaving
      servers warn the group that they are leaving, one by one, then the
      membership is able to adjust itself from 5 to 2, and at the same
      time, securing quorum while that happens.
  </p>
  <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
   <div class="admon-title">
    Note
   </div>
   <p>
    Loss of quorum is by itself a side-effect of bad planning. Plan
        the group size for the number of expected failures (regardless
        whether they are consecutive, happen all at once or are
        sporadic).
   </p>
  </div>
  <p>
   For a group in single-primary mode, the primary might have
      transactions that are not yet present on other members at the time
      of the network partition. If you are considering excluding the
      primary from the new group, be aware that such transactions might
      be lost. A member with extra transactions cannot rejoin the group,
      and the attempt results in an error with the message
   <span class="errortext">
    This member has more executed transactions than those
      present in the group
   </span>
   . Set the
   <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_unreachable_majority_timeout">
    <code class="literal">
     group_replication_unreachable_majority_timeout
    </code>
   </a>
   system variable for the group members to avoid this situation.
  </p>
  <p>
   The following sections explain what to do if the system partitions
      in such a way that no quorum is automatically achieved by the
      servers in the group.
  </p>
  <div class="simplesect">
   <div class="titlepage">
    <div>
     <div class="simple">
      <h4 class="title">
       <a name="group-replication-detecting-partitions">
       </a>
       Detecting Partitions
      </h4>
     </div>
    </div>
   </div>
   <p>
    The
    <a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table">
     <code class="literal">
      replication_group_members
     </code>
    </a>
    performance schema table presents the status of each server in
        the current view from the perspective of this server. The
        majority of the time the system does not run into partitioning,
        and therefore the table shows information that is consistent
        across all servers in the group. In other words, the status of
        each server on this table is agreed by all in the current view.
        However, if there is network partitioning, and quorum is lost,
        then the table shows the status
    <code class="literal">
     UNREACHABLE
    </code>
    for those servers that it cannot contact. This information is
        exported by the local failure detector built into Group
        Replication.
   </p>
   <div class="figure">
    <a name="idm46045131874944">
    </a>
    <p class="title">
     <b>
      Figure 20.14 Losing Quorum
     </b>
    </p>
    <div class="figure-contents">
     <div class="mediaobject">
      <img alt="Five server instances, S1, S2, S3, S4, and S5, are deployed as an interconnected group, which is a stable group. When three of the servers, S3, S4, and S5, fail, the majority is lost and the group can no longer proceed without intervention." src="images/gr-majority-lost.png" style="width: 100%; max-width: 243px;"/>
     </div>
    </div>
   </div>
   <br class="figure-break"/>
   <p>
    To understand this type of network partition the following
        section describes a scenario where there are initially 5 servers
        working together correctly, and the changes that then happen to
        the group once only 2 servers are online. The scenario is
        depicted in the

        

        figure.
   </p>
   <p>
    As such, lets assume that there is a group with these 5 servers
        in it:
   </p>
   <div class="itemizedlist">
    <ul class="itemizedlist" style="list-style-type: disc; ">
     <li class="listitem">
      <p>
       Server s1 with member identifier
       <code class="literal">
        199b2df7-4aaf-11e6-bb16-28b2bd168d07
       </code>
      </p>
     </li>
     <li class="listitem">
      <p>
       Server s2 with member identifier
       <code class="literal">
        199bb88e-4aaf-11e6-babe-28b2bd168d07
       </code>
      </p>
     </li>
     <li class="listitem">
      <p>
       Server s3 with member identifier
       <code class="literal">
        1999b9fb-4aaf-11e6-bb54-28b2bd168d07
       </code>
      </p>
     </li>
     <li class="listitem">
      <p>
       Server s4 with member identifier
       <code class="literal">
        19ab72fc-4aaf-11e6-bb51-28b2bd168d07
       </code>
      </p>
     </li>
     <li class="listitem">
      <p>
       Server s5 with member identifier
       <code class="literal">
        19b33846-4aaf-11e6-ba81-28b2bd168d07
       </code>
      </p>
     </li>
    </ul>
   </div>
   <p>
    Initially the group is running fine and the servers are happily
        communicating with each other. You can verify this by logging
        into s1 and looking at its
    <a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table">
     <code class="literal">
      replication_group_members
     </code>
    </a>
    performance schema table. For example:
   </p>
   <div class="copytoclipboard-wrapper">
    <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa5590121"><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> MEMBER_ID<span class="token punctuation">,</span>MEMBER_STATE<span class="token punctuation">,</span> MEMBER_ROLE <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="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> MEMBER_ID                            <span class="token punctuation">|</span> MEMBER_STATE <span class="token punctuation">|</span> MEMBER_ROLE <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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="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> 1999b9fb<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb54<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <span class="token punctuation">|</span> SECONDARY   <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199b2df7<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb16<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <span class="token punctuation">|</span> PRIMARY     <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199bb88e<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>babe<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <span class="token punctuation">|</span> SECONDARY   <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19ab72fc<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb51<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <span class="token punctuation">|</span> SECONDARY   <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19b33846<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>ba81<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <span class="token punctuation">|</span> SECONDARY   <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 class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="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>
    However, moments later there is a catastrophic failure and
        servers s3, s4 and s5 stop unexpectedly. A few seconds after
        this, looking again at the
    <a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table">
     <code class="literal">
      replication_group_members
     </code>
    </a>
    table on
        s1 shows that it is still online, but several others members are
        not. In fact, as seen below they are marked as
    <code class="literal">
     UNREACHABLE
    </code>
    . Moreover, the system could not
        reconfigure itself to change the membership, because the
        majority has been lost.
   </p>
   <div class="copytoclipboard-wrapper">
    <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa81705083"><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> MEMBER_ID<span class="token punctuation">,</span>MEMBER_STATE <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<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>
<span class="token output"><span class="token punctuation">|</span> MEMBER_ID                            <span class="token punctuation">|</span> MEMBER_STATE <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>
<span class="token output"><span class="token punctuation">|</span> 1999b9fb<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb54<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE  <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199b2df7<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb16<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199bb88e<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>babe<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19ab72fc<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb51<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE  <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19b33846<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>ba81<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE  <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></code></pre>
   </div>
   <p>
    The table shows that s1 is now in a group that has no means of
        progressing without external intervention, because a majority of
        the servers are unreachable. In this particular case, the group
        membership list needs to be reset to allow the system to
        proceed, which is explained in this section. Alternatively, you
        could also choose to stop Group Replication on s1 and s2 (or
        stop completely s1 and s2), figure out what happened with s3, s4
        and s5 and then restart Group Replication (or the servers).
   </p>
  </div>
  <div class="simplesect">
   <div class="titlepage">
    <div>
     <div class="simple">
      <h4 class="title">
       <a name="group-replication-unblocking-a-partition">
       </a>
       Unblocking a Partition
      </h4>
     </div>
    </div>
   </div>
   <p>
    Group replication enables you to reset the group membership list
        by forcing a specific configuration. For instance in the case
        above, where s1 and s2 are the only servers online, you could
        choose to force a membership configuration consisting of only s1
        and s2. This requires checking some information about s1 and s2
        and then using the
    <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_force_members">
     <code class="literal">
      group_replication_force_members
     </code>
    </a>
    variable.
   </p>
   <div class="figure">
    <a name="idm46045131843632">
    </a>
    <p class="title">
     <b>
      Figure 20.15 Forcing a New Membership
     </b>
    </p>
    <div class="figure-contents">
     <div class="mediaobject">
      <img alt="Three of the servers in a group, S3, S4, and S5, have failed, so the majority is lost and the group can no longer proceed without intervention. With the intervention described in the following text, S1 and S2 are able to form a stable group by themselves." src="images/gr-majority-lost-to-stable-group.png" style="width: 100%; max-width: 243px;"/>
     </div>
    </div>
   </div>
   <br class="figure-break"/>
   <p>
    Suppose that you are back in the situation where s1 and s2 are
        the only servers left in the group. Servers s3, s4 and s5 have
        left the group unexpectedly. To make servers s1 and s2 continue,
        you want to force a membership configuration that contains only
        s1 and s2.
   </p>
   <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
    <div class="admon-title">
     Warning
    </div>
    <p>
     This procedure uses
     <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_force_members">
      <code class="literal">
       group_replication_force_members
      </code>
     </a>
     and should be considered a last resort remedy. It
     <span class="emphasis">
      <em>
       must
      </em>
     </span>
     be used with extreme care and only
          for overriding loss of quorum. If misused, it could create an
          artificial split-brain scenario or block the entire system
          altogether.
    </p>
   </div>
   <p>
    When forcing a new membership configuration, make sure that any
        servers are going to be forced out of the group are indeed
        stopped. In the scenario depicted above, if s3, s4 and s5 are
        not really unreachable but instead are online, they may have
        formed their own functional partition (they are 3 out of 5,
        hence they have the majority). In that case, forcing a group
        membership list with s1 and s2 could create an artificial
        split-brain situation. Therefore it is important before forcing
        a new membership configuration to ensure that the servers to be
        excluded are indeed shut down and if they are not, shut them
        down before proceeding.
   </p>
   <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
    <div class="admon-title">
     Warning
    </div>
    <p>
     For a group in single-primary mode, the primary might have
          transactions that are not yet present on other members at the
          time of the network partition. If you are considering
          excluding the primary from the new group, be aware that such
          transactions might be lost. A member with extra transactions
          cannot rejoin the group, and the attempt results in an error
          with the message
     <span class="errortext">
      This member has more executed
          transactions than those present in the group
     </span>
     . Set
          the
     <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_unreachable_majority_timeout">
      <code class="literal">
       group_replication_unreachable_majority_timeout
      </code>
     </a>
     system variable for the group members to avoid this situation.
    </p>
   </div>
   <p>
    Recall that the system is blocked and the current configuration
        is the following (as perceived by the local failure detector on
        s1):
   </p>
   <div class="copytoclipboard-wrapper">
    <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa45391294"><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> MEMBER_ID<span class="token punctuation">,</span>MEMBER_STATE <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<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>
<span class="token output"><span class="token punctuation">|</span> MEMBER_ID                            <span class="token punctuation">|</span> MEMBER_STATE <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>
<span class="token output"><span class="token punctuation">|</span> 1999b9fb<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb54<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE  <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199b2df7<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb16<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 199bb88e<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>babe<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19ab72fc<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>bb51<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE  <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 19b33846<span class="token punctuation">-</span>4aaf<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>ba81<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> UNREACHABLE  <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></code></pre>
   </div>
   <p>
    The first thing to do is to check what is the local address
        (group communication identifier) for s1 and s2. Log in to s1 and
        s2 and get that information as follows.
   </p>
   <div class="copytoclipboard-wrapper">
    <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa67979432"><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">@@group_replication_local_address</span><span class="token punctuation">;</span></code></pre>
   </div>
   <p>
    Once you know the group communication addresses of s1
        (
    <code class="literal">
     127.0.0.1:10000
    </code>
    ) and s2
        (
    <code class="literal">
     127.0.0.1:10001
    </code>
    ), you can use that on one of
        the two servers to inject a new membership configuration, thus
        overriding the existing one that has lost quorum. To do that on
        s1:
   </p>
   <div class="copytoclipboard-wrapper">
    <pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa9550509"><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 keyword">GLOBAL</span> group_replication_force_members<span class="token operator">=</span><span class="token string">"127.0.0.1:10000,127.0.0.1:10001"</span><span class="token punctuation">;</span></code></pre>
   </div>
   <p>
    This unblocks the group by forcing a different configuration.
        Check
    <a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table">
     <code class="literal">
      replication_group_members
     </code>
    </a>
    on
        both s1 and s2 to verify the group membership after this change.
        First on s1.
   </p>
   <div class="copytoclipboard-wrapper">
    <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa41302978"><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> MEMBER_ID<span class="token punctuation">,</span>MEMBER_STATE <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<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>
<span class="token output"><span class="token punctuation">|</span> MEMBER_ID                            <span class="token punctuation">|</span> MEMBER_STATE <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>
<span class="token output"><span class="token punctuation">|</span> b5ffe505<span class="token punctuation">-</span>4ab6<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>b04b<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> b60907e7<span class="token punctuation">-</span>4ab6<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>afb7<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <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></code></pre>
   </div>
   <p>
    And then on s2.
   </p>
   <div class="copytoclipboard-wrapper">
    <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa64059566"><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 operator">*</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<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>
<span class="token output"><span class="token punctuation">|</span> MEMBER_ID                            <span class="token punctuation">|</span> MEMBER_STATE <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>
<span class="token output"><span class="token punctuation">|</span> b5ffe505<span class="token punctuation">-</span>4ab6<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>b04b<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> b60907e7<span class="token punctuation">-</span>4ab6<span class="token punctuation">-</span>11e6<span class="token punctuation">-</span>afb7<span class="token punctuation">-</span>28b2bd168d07 <span class="token punctuation">|</span> ONLINE       <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></code></pre>
   </div>
   <p>
    After you have used the
    <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_force_members">
     <code class="literal">
      group_replication_force_members
     </code>
    </a>
    system variable to successfully force a new group membership and
        unblock the group, ensure that you clear the system variable.
    <a class="link" href="group-replication-system-variables.html#sysvar_group_replication_force_members">
     <code class="literal">
      group_replication_force_members
     </code>
    </a>
    must be empty in order to issue a
    <a class="link" href="start-group-replication.html" title="15.4.3.1 START GROUP_REPLICATION Statement">
     <code class="literal">
      START
        GROUP_REPLICATION
     </code>
    </a>
    statement.
   </p>
  </div>
 </div>
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</div>
