78 lines
5.6 KiB
HTML
78 lines
5.6 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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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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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Resilient applications" />
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<meta name="abstract" content="A resilient application is an application that can be restarted on a different cluster node without requiring you to reconfigure the clients." />
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<meta name="description" content="A resilient application is an application that can be restarted on a different cluster node without requiring you to reconfigure the clients." />
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<meta name="DC.Relation" scheme="URI" content="rzaigconceptsresilientresources.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzaigapplicationsmakeappsresilient.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzaigconceptsrecoverydomain.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzaigapplications.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Resilient applications</title>
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</head>
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<body id="rzaigconceptsresilientapplications"><a name="rzaigconceptsresilientapplications"><!-- --></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">Resilient applications</h1>
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<div><p>A <dfn class="term">resilient application</dfn> is an application
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that can be restarted on a different cluster node without requiring you to
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reconfigure the clients.</p>
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<p>See Making application programs resilient to learn about what characteristics
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make an application resilient.</p>
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<p>A resilient application needs the ability to recognize the temporary loss
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of the Internet Protocol (IP) connection between the client and the server.
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The client application must be aware that the IP connection will be temporarily
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unavailable and must retry access rather than ending or initiating a failover.
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Similarly, if you are performing a switchover, server applications need to
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be aware that the IP connection is no longer available. Eventually, an error
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condition is returned to the server application. Once this error condition
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is received, it is best if the server application recognizes the condition
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and ends normally.</p>
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<p>IP address takeover is a high availability function that is used to protect
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clients from application server outages. An <span class="uicontrol">application takeover
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IP address</span> is a floating address that is to be associated with
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an application. The concept is to use IP address aliasing to define a floating
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IP address that is associated with multiple application servers or hosts.
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When one application server in a cluster fails, another cluster node assumes
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the responsibilities of the application server without requiring you to reconfigure
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the clients.</p>
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<p>Also introduced in support of IP address takeover is the concept of application
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cluster resource groups (CRGs). Application CRGs are cluster resource groups
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that contain an application takeover IP address resource and a recovery domain.
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The recovery domain contains the list of application servers within the cluster
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that support a particular application. If a single resource fails, cluster
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resource services initiates a failover on the group to which the failing resource
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belongs.</p>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaigconceptsresilientresources.htm" title="Resilient resources are system resources, such as data, devices and applications, that are highly available if you have used clustering on your systems.">Resilient resources</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="rzaigapplicationsmakeappsresilient.htm" title="Learn how to make application programs resilient.">Make application programs resilient</a></div>
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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>
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<div class="reltasks"><strong>Related tasks</strong><br />
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<div><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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</div>
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</body>
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</html>
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