134 lines
9.9 KiB
HTML
134 lines
9.9 KiB
HTML
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<meta name="DC.Title" content="Partition errors" />
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<meta name="abstract" content="Certain cluster conditions are easily corrected. If a cluster partition has occurred, you can learn how to recover. This topic also tells you how to avoid a cluster partition and gives you an example of how to merge partitions back together." />
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<title>Partition errors</title>
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<body id="rzaigtroubleshootpartitionerrors"><a name="rzaigtroubleshootpartitionerrors"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Partition errors</h1>
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<div><p>Certain cluster conditions are easily corrected. If a cluster partition
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has occurred, you can learn how to recover. This topic also tells you how
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to avoid a cluster partition and gives you an example of how to merge partitions
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back together.</p>
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<p>A cluster partition occurs in a cluster whenever contact is lost between
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one or more nodes in the cluster and a failure of the lost nodes cannot be
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confirmed. This is not to be confused with a partition in a logical partition
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(LPAR) environment.</p>
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<p>If you receive error message CPFBB20 in either the history log (QHST) or
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the QCSTCTL joblog, a cluster partition has occurred and you need to know
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how to recover. The following example shows a cluster partition that involves
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a cluster made up of four nodes: A, B, C, and D. The example shows a loss
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of communication between cluster nodes B and C has occurred, which results
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in the cluster dividing into two cluster partitions. Before the cluster partition
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occurred, there were four cluster resource groups, which can be of any type,
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called CRG A, CRG B, CRG C, and CRG D. The example shows the recovery domain
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of each cluster resource group.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><caption>Table 1. Example of a recovery domain during a cluster partition</caption><thead align="left"><tr valign="bottom"><th align="center" valign="bottom" width="24%" id="d0e36">Node A</th>
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<th align="center" valign="bottom" width="24%" id="d0e38">Node B</th>
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<th align="center" valign="bottom" width="4%" id="d0e40">x</th>
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<th align="center" valign="bottom" width="24%" id="d0e42">Node C</th>
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<th align="center" valign="bottom" width="24%" id="d0e44">Node D</th>
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</tr>
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</thead>
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<tbody><tr><td align="center" valign="top" width="24%" headers="d0e36 ">CRG A (backup1)</td>
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<td align="center" valign="top" width="24%" headers="d0e38 ">CRG A (primary)</td>
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<td rowspan="4" valign="top" width="4%" headers="d0e40 "> </td>
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<td align="center" valign="top" width="24%" headers="d0e42 "> </td>
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<td align="center" valign="top" width="24%" headers="d0e44 "> </td>
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</tr>
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<tr><td align="center" valign="top" width="24%" headers="d0e36 "> </td>
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<td align="center" valign="top" width="24%" headers="d0e38 ">CRG B (primary)</td>
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<td align="center" valign="top" width="24%" headers="d0e42 ">CRG B (backup1)</td>
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<td align="center" valign="top" width="24%" headers="d0e44 "> </td>
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</tr>
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<tr><td align="center" valign="top" width="24%" headers="d0e36 "> </td>
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<td align="center" valign="top" width="24%" headers="d0e38 ">CRG C (primary)</td>
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<td align="center" valign="top" width="24%" headers="d0e42 ">CRG C (backup1)</td>
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<td align="center" valign="top" width="24%" headers="d0e44 ">CRG C (backup2)</td>
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</tr>
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<tr><td align="center" valign="top" width="24%" headers="d0e36 ">CRG D (backup2)</td>
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<td align="center" valign="top" width="24%" headers="d0e38 ">CRG D (primary)</td>
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<td align="center" valign="top" width="24%" headers="d0e42 ">CRG D (backup1)</td>
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<td align="center" valign="top" width="24%" headers="d0e44 "> </td>
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</tr>
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<tr><td colspan="2" align="center" valign="top" headers="d0e36 d0e38 "><strong>Partition 1</strong></td>
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<td align="center" valign="top" width="4%" headers="d0e40 "> </td>
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<td colspan="2" align="center" valign="top" headers="d0e42 d0e44 "><strong>Partition 2</strong></td>
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</tr>
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</tbody>
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</table>
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</div>
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<p>A cluster may partition if the maximum transmission unit (MTU) at any point
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in the communication path is less than the cluster communications tuneable
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parameter, message fragment size. MTU for a cluster IP address can be verified
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using the <span class="cmdname">Work with TCP/IP Network Status (WRKTCPSTS)</span> command
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on the subject node. The MTU must also be verified at each step along the
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entire communication path. If the MTU is less than the message fragment size,
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either raise the MTU of the path or lower the message fragment size. You can
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use the <span class="apiname">Retrieve Cluster Resource Services Information (QcstRetrieveCRSInfo)</span> API
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to view the current settings of the tuning parameters and the<span class="apiname"> Change
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Cluster Resource Services (QcstChgClusterResourceServices)</span> API to
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change the settings.</p>
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<p>Once the cause of the cluster partition condition has been corrected, the
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cluster will detect the re-established communication link and issue the message
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CPFBB21 in either the history log (QHST) or the QCSTCTL joblog. This informs
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the operator that the cluster has recovered from the cluster partition. Be
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aware that once the cluster partition condition has been corrected, it may
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be a few minutes before the cluster merges back together.</p>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rzaigtroubleshootdeterminepartitions.htm">Determine primary and secondary cluster partitions</a></strong><br />
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<span><img src="./delta.gif" alt="Start of change" />In order to determine the types of cluster resource
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group actions that you can take within a cluster partition, you need to know
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whether the partition is a primary or a secondary cluster partition. When
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a partition is detected, each partition is designated as a primary or secondary
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partition for each cluster resource group defined in the cluster.<img src="./deltaend.gif" alt="End of change" /></span></li>
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<li class="ulchildlink"><strong><a href="rzaigtroubleshootchangepartitionednodes.htm">Change partitioned nodes to failed</a></strong><br />
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Sometimes, a partitioned condition is reported when there really was a node outage. This can occur when cluster resource services loses communications with one or more nodes, but cannot detect if the nodes are still operational. When this condition occurs, a simple mechanism exists for you to indicate that the node has failed.</li>
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<li class="ulchildlink"><strong><a href="rzaigtroubleshoottipclusterpartitions.htm">Tips: Cluster partitions</a></strong><br />
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Use these tips for cluster partitions.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaigtroubleshoot.htm" title="Find error recovery solutions for problems that are specific to clusters.">Troubleshoot clusters</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rzaigconceptpartition.htm" title="A cluster partition is a subset of the active cluster nodes that results from a communications failure. Members of a partition maintain connectivity with each other.">Cluster partition</a></div>
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<div><a href="rzaigplanavoidclusterpartition.htm" title="The typical network-related cluster partition can best be avoided by configuring redundant communications paths between all nodes in the cluster.">Avoid a cluster partition</a></div>
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<div><a href="rzaigconceptsmerge.htm" title="A merge operation is similar to a rejoin operation except that it occurs when nodes that are partitioned begin communicating again.">Merge</a></div>
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<div><a href="rzaigtroubleshootexamplefailover.htm" title="Usually, a failover results from a node failure, but there are other reasons that can also generate a failover.">Example: Failure</a></div>
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</div>
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</div>
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