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     <h3 class="title">
      <a name="mysql-cluster-upgrade-downgrade">
      </a>
      25.3.7 Upgrading and Downgrading NDB Cluster
     </h3>
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     <p>
      <a class="xref" href="mysql-cluster-upgrade-downgrade.html#mysql-cluster-upgrade-versions" title="Versions Supported for Upgrade to NDB 8.4">
       Versions Supported for Upgrade to NDB 8.4
      </a>
     </p>
    </li>
    <li class="listitem">
     <p>
      <a class="xref" href="mysql-cluster-upgrade-downgrade.html#mysql-cluster-updowngrade-issues" title="Known Issues When Upgrading or Downgrading NDB Cluster">
       Known Issues When Upgrading or Downgrading NDB Cluster
      </a>
     </p>
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  <p>
   This section provides information about NDB Cluster software and
      compatibility between different NDB Cluster releases with regard
      to performing upgrades and downgrades. You should already be
      familiar with installing and configuring NDB Cluster prior to
      attempting an upgrade or downgrade. See
   <a class="xref" href="mysql-cluster-configuration.html" title="25.4 Configuration of NDB Cluster">
    Section 25.4, “Configuration of NDB Cluster”
   </a>
   .
  </p>
  <p>
   For information about upgrades to NDB 8.4 from
      previous versions, see
   <a class="xref" href="mysql-cluster-upgrade-downgrade.html#mysql-cluster-upgrade-versions" title="Versions Supported for Upgrade to NDB 8.4">
    Versions Supported for Upgrade to NDB 8.4
   </a>
   .
  </p>
  <p>
   For information about known issues and problems encountered when
      upgrading or downgrading NDB 8.4, see
   <a class="xref" href="mysql-cluster-upgrade-downgrade.html#mysql-cluster-updowngrade-issues" title="Known Issues When Upgrading or Downgrading NDB Cluster">
    Known Issues When Upgrading or Downgrading NDB Cluster
   </a>
   .
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     <div class="simple">
      <h4 class="title">
       <a name="mysql-cluster-upgrade-versions">
       </a>
       Versions Supported for Upgrade to NDB 8.4
      </h4>
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   <p>
    The following versions of NDB Cluster are supported for upgrades
        to NDB Cluster 8.4:
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      <p>
       NDB Cluster 8.0: NDB 8.0.19 and later
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     </li>
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      <p>
       NDB Cluster 8.1 (8.1.0)
      </p>
     </li>
     <li class="listitem">
      <p>
       NDB Cluster 8.2 (8.2.0)
      </p>
     </li>
     <li class="listitem">
      <p>
       NDB Cluster 8.3 (8.3.0)
      </p>
     </li>
    </ul>
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     <div class="simple">
      <h4 class="title">
       <a name="mysql-cluster-updowngrade-issues">
       </a>
       Known Issues When Upgrading or Downgrading NDB Cluster
      </h4>
     </div>
    </div>
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   <p>
    In this section, provide information about issues known to occur
        when upgrading or downgrading to or from NDB 8.4.
   </p>
   <p>
    We recommend that you not attempt any schema changes during any
        NDB Cluster software upgrade or downgrade. Some of the reasons
        for this are listed here:
   </p>
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      <p>
       DDL statements on
       <code class="literal">
        NDB
       </code>
       tables are not
            possible during some phases of data node startup.
      </p>
     </li>
     <li class="listitem">
      <p>
       DDL statements on
       <code class="literal">
        NDB
       </code>
       tables may be
            rejected if any data nodes are stopped during execution;
            stopping each data node binary (so it can be replaced with a
            binary from the target version) is required as part of the
            upgrade or downgrade process.
      </p>
     </li>
     <li class="listitem">
      <p>
       DDL statements on
       <code class="literal">
        NDB
       </code>
       tables are not
            allowed while there are data nodes in the same cluster
            running different release versions of the NDB Cluster
            software.
      </p>
     </li>
    </ul>
   </div>
   <p>
    For additional information regarding the rolling restart
        procedure used to perform an online upgrade or downgrade of the
        data nodes, see
    <a class="xref" href="mysql-cluster-rolling-restart.html" title="25.6.5 Performing a Rolling Restart of an NDB Cluster">
     Section 25.6.5, “Performing a Rolling Restart of an NDB Cluster”
    </a>
    .
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