74 lines
5.6 KiB
HTML
74 lines
5.6 KiB
HTML
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Failover" />
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<meta name="abstract" content="Failover occurs when a server in a cluster automatically switches over to one or more backup servers in the event of a system failure." />
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<meta name="description" content="Failover occurs when a server in a cluster automatically switches over to one or more backup servers in the event of a system failure." />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<title>Failover</title>
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</head>
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<body id="rzaigconceptsfailover"><a name="rzaigconceptsfailover"><!-- --></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">Failover</h1>
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<div><p><dfn class="term">Failover</dfn> occurs when a server in a cluster
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automatically switches over to one or more backup servers in the event of
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a system failure.</p>
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<p>Contrast this with a switchover, which happens when you manually switch
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access from one server to another. A switchover and a failover function identically
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once they have been triggered. The only difference is how the event is triggered.</p>
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<p>When a failover occurs, access is switched from the cluster node currently
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acting as the primary node in the recovery domain of the cluster resource
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group to the cluster node designated as the first backup. See recovery domain
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for information about how the switchover order is determined.</p>
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<p>When multiple cluster resource groups (CRGs) are involved in a failover
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action, the system processes the device CRGs (switchable devices) first, the
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data CRGs (switchable data groups) second, and the application CRGs (switchable
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applications) last.</p>
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<p>The failover message queue receives messages regarding failover activity.
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You can use it to control the failover processing of a cluster resource group.</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"><img src="./delta.gif" alt="Start of change" /><strong><a href="rzaigtroubleshootexamplefailover.htm">Example: Failure</a></strong><img src="./deltaend.gif" alt="End of change" /><br />
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Usually, a failover results from a node failure, but there are other reasons that can also generate a failover.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <img src="./delta.gif" alt="Start of change" /><a href="rzaigconceptsevents.htm" title="Within a cluster several types events, actions, and services can occur.">Cluster events</a><img src="./deltaend.gif" alt="End of change" /></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="rzaigconceptsrecoverydomain.htm" title="A recovery domain is a subset of cluster nodes that are grouped together in a cluster resource group (CRG) for a common purpose such as performing a recovery action or synchronizing events.">Recovery domain</a></div>
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<div><a href="rzaigconceptscrg.htm" title="A cluster resource group (CRG) is an i5/OS system object that is a set or grouping of cluster resources that are used to manage events that occur in a clustered environment. The cluster resource group describes a recovery domain and supplies the name of the cluster resource group exit program which gets called when certain cluster events occur.">Cluster resource group</a></div>
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<div><a href="rzaigconceptsfailovermessagequeue.htm" title="The failover message queue receives messages regarding failover activity.">Failover message queue</a></div>
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<div><a href="rzaigplanhardware.htm" title="Any iSeries model that is capable of running i5/OS V4R4M0 or later is compatible for using clustering.">Hardware requirements for clusters</a></div>
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</div>
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<div class="reltasks"><strong>Related tasks</strong><br />
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<div><a href="rzaigconceptsswitchover.htm" title="Switchover happens when you manually switch access to a resource from one server to another.">Switchover</a></div>
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</div>
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</div>
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