93 lines
6.2 KiB
HTML
93 lines
6.2 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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<html lang="en-us" xml:lang="en-us">
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Journal access paths" />
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<meta name="abstract" content="Journaling access paths can significantly reduce recovery time by reducing the number of access paths that need to be rebuilt after an abnormal system end. It is recommended that you journal access paths because larger access paths require more time to rebuild." />
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<meta name="description" content="Journaling access paths can significantly reduce recovery time by reducing the number of access paths that need to be rebuilt after an abnormal system end. It is recommended that you journal access paths because larger access paths require more time to rebuild." />
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<meta name="DC.Relation" scheme="URI" content="rbaforzahfpri.htm" />
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<meta name="DC.Relation" scheme="URI" content="../cl/strjrnap.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<title>Journal access paths</title>
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</head>
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<body id="rbaforzahfprl"><a name="rbaforzahfprl"><!-- --></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">Journal access paths</h1>
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<div><p>Journaling access paths can significantly reduce recovery time
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by reducing the number of access paths that need to be rebuilt after an abnormal
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system end. It is recommended that you journal access paths because larger
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access paths require more time to rebuild.</p>
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<p>When you journal database files, you record images of changes to the file
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in the journal. The system uses these record images to recover the file after
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an abnormal system end. </p>
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<p>After an abnormal end, the system might find that access paths are not
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synchronized with the data in the file. If an access path does not synchronize
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with its data, the system rebuilds the access path to ensure that the two
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are synchronized and usable.</p>
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<p>When journaling access paths, the system records images of the access path
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in the journal to provide known synchronization points between the access
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path and its data. By having that information in the journal, the system recovers
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both the data files and the access paths. The system then synchronizes the
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two. In such cases, you avoid the lengthy time to rebuild access paths.</p>
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<p>In addition, other system recovery functions work with journaling access
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paths. For example, the system has a number of options to reduce recovery
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time from the failure and replacement of a disk unit. These options include
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user auxiliary storage pools and checksum protection. These options further
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reduce the chances that the entire system must reload because of the disk
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failure. However, you might still need to rebuild access paths when the system
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is started following replacement of the failed disk. By using access path
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journaling and some of the recovery options, you reduce your chances of having
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to reload the entire system and having to rebuild access paths.</p>
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<div class="p">Before journaling an access path, you must journal the physical files that
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are associated with the access path. In addition, you must use the same journal
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for the access path and its associated physical files. It is easy to start
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journaling access paths:<ul><li>You can use the system-managed access-path protection (SMAPP) facility.</li>
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<li>You can manage the journaling environment yourself with the Start Journal
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Access Path (STRJRNAP) command. <ul><li>To start journaling the access path for the specified file, use the STRJRNAP
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command. You can journal access paths that have a maintenance attribute of
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immediate (*IMMED) or delayed (*DLY).</li>
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<li>After you start journaling, the system protects the access path until
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the access path is deleted or until you run the End Journal Access Path (ENDJRNAP)
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command for that access path.</li>
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</ul>
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</li>
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</ul>
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</div>
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<p>Access path journaling minimizes additional output operations. For example,
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the system will write the journal data for the changed record and the changed
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access path in the same output operation. However, you should seriously consider
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isolating your journal receivers in user auxiliary storage pools when you
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start journaling your access paths. Placing journal receivers in their own
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user auxiliary storage pool provides the best journaling performance, while
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helping to protect them from a disk failure.</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="rbaforzahfpri.htm" title="The system ensures the integrity of an access path before you can use it. If the system determines that the access path is unusable, the system attempts to recover it. You can control when to have the access path recovered.">Reduce time in access path recovery</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="../rzaki/rzakikickoff.htm">Journal management</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="../cl/strjrnap.htm">Start Journal Access Path (STRJRNAP) command</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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