63 lines
4.0 KiB
HTML
63 lines
4.0 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 http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="security" content="public" />
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<meta name="Robots" content="index,follow" />
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Restore access paths" />
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<meta name="abstract" content="The system has the ability to restore access paths and it usually restores an access path faster than it rebuilds it." />
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<meta name="description" content="The system has the ability to restore access paths and it usually restores an access path faster than it rebuilds it." />
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<meta name="DC.Relation" scheme="URI" content="rbaforzahfpri.htm" />
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<meta name="DC.Relation" scheme="URI" content="../rzaki/rzakikickoff.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="rbaforzahfprk" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Restore access paths</title>
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</head>
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<body id="rbaforzahfprk"><a name="rbaforzahfprk"><!-- --></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">Restore access paths</h1>
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<div><p>The system has the ability to restore access paths and it usually
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restores an access path faster than it rebuilds it.</p>
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<div class="p">The system can restore access paths if: <ul><li>They were previously saved.</li>
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<li>All the physical files on which they depend are restored at the same time.</li>
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</ul>
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</div>
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<p>For example, assume that a logical file is built over a physical file that
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contains 500 000 records. You have determined through the Display Object Description
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(DSPOBJD) command that the size of the logical file is about 15 megabytes. </p>
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<p>In this example, it takes about 50 minutes to rebuild the access path for
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the logical file. It takes about 1 minute to restore the same access path
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from a tape. (This assumes that the system builds approximately 10 000 index
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entries per minute.)</p>
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<p>After restoring the access path, you might need to update the file by applying
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the latest journal changes. For example, the system applies approximately
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80 000 to 100 000 journal entries to the file per hour. This assumes that
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each of the physical files to which entries are being applied has only one
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access path built over it. This rate drops proportionally for each access
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path of *IMMED maintenance that is present over the physical file. Even with
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this additional recovery time, you usually find that it is faster to restore
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access paths than to rebuild them.</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>
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</body>
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</html>
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