76 lines
5.3 KiB
HTML
76 lines
5.3 KiB
HTML
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<meta name="DC.Title" content="Writing a highly available cluster application" />
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<meta name="abstract" content="A highly available application is one that can be resilient to a system outage in a clustered environment." />
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<title>Writing a highly available cluster application</title>
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<body id="rzaigapplicationswritehighlyavailable"><a name="rzaigapplicationswritehighlyavailable"><!-- --></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">Writing a highly available cluster application</h1>
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<div><p>A highly available application is one that can be resilient to
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a system outage in a clustered environment.</p>
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<div class="section">Several levels of application availability are possible:</div>
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<ol><li class="stepexpand"><span>If an application error occurs, the application restarts itself
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on the same node and corrects any potential cause for error (such as corrupt
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control data). You can view the application as though it had started for
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the first time.</span></li>
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<li class="stepexpand"><span>The application performs some amount of checkpoint-restart processing.
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You can view the application as if it were close to the point of failure.</span></li>
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<li class="stepexpand"><span>If a system outage occurs, the application is restarted on a backup
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server. You can view the application as though it had started for the first
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time.</span></li>
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<li class="stepexpand"><span>If a system outage occurs, the application is restarted on a backup
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server and performs some amount of checkpoint-restart processing across the
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servers. You can view the application as if it were close to the point of
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failure.</span></li>
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<li class="stepexpand"><span>If a system outage occurs, a coordinated failover of both the application
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and its associated data to another node or nodes in the cluster occurs. You can view the application as though it had started for the first
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time.</span></li>
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<li class="stepexpand"><span>If a system outage occurs, a coordinated failover of both the application
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and its associated data to another node or nodes in the cluster occurs. The application performs some amount of checkpoint-restart processing
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across the servers. You can view the application as if it were close to
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the point of failure.</span> <div class="note"><span class="notetitle">Note:</span> In cases 1 through 4 above, you are
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responsible for recovering the data.</div>
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</li>
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</ol>
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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="rzaigapplicationsmakeappsresilient.htm">Make application programs resilient</a></strong><br />
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Learn how to make application programs resilient.</li>
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<li class="ulchildlink"><strong><a href="rzaigapplicationsrestart.htm">Restart highly available cluster applications</a></strong><br />
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To restart an application, the application needs to know its state at the time of the failover or switchover.</li>
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<li class="ulchildlink"><strong><a href="rzaigapplicationscallcrgexitprogram.htm">Calling a cluster resource group exit program</a></strong><br />
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The cluster resource group exit program is called during different phases of a cluster environment.</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="rzaigapplications.htm" title="Application resilience is one of the key elements in a clustered environment. If you are planning to write and use highly available applications in your cluster you should be aware that these applications have specific availability specifications.">Cluster applications</a></div>
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</div>
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</body>
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