67 lines
4.5 KiB
HTML
67 lines
4.5 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.Title" content="Other methods to avoid rebuilding access paths" />
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<meta name="abstract" content="If you do not journal your access paths or do not take advantage of system-managed access-path protection (SMAPP), consider other system functions that reduce the chances of rebuilding access paths." />
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<meta name="description" content="If you do not journal your access paths or do not take advantage of system-managed access-path protection (SMAPP), consider other system functions that reduce the chances of rebuilding access paths." />
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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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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<title>Other methods to avoid rebuilding access paths</title>
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</head>
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<body id="rbaforzahfprr"><a name="rbaforzahfprr"><!-- --></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">Other methods to avoid rebuilding access paths</h1>
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<div><p>If you do not journal your access paths or do not take advantage
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of system-managed access-path protection (SMAPP), consider other
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system functions that reduce the chances of rebuilding access paths. </p>
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<p>The system uses a file synchronization indicator to determine if an access
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path needs to be rebuilt. Normally, the synchronization indicator is on, indicating
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the synchronization of the access path and its associated data. When a job
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changes a file that affects an access path, the system turns off the synchronization
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indicator in the file. If the system ends abnormally, it must rebuild any
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access path whose file has its synchronization indicator off.</p>
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<p>You need to periodically synchronize the data with its access path to reduce
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the number of access paths you must rebuild. There are several methods to
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synchronize a file with its access path:</p>
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<ul><li>Full file close. The last full (that is, not shared) system-wide close
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performed against a file will synchronize the access path and the data.</li>
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<li>Force access path. Specify the force-access-path (FRCACCPTH) parameter
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on the create, change, or override database file commands.</li>
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<li>Force write ratio of 2 or greater. Specify the force-write-ratio (FRCRATIO)
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parameter on the create, change, or override database file commands.</li>
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<li>Force end of data. Running the force-end-of-data operation in your program
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can synchronize the file's data and its access path. (Some high-level languages
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do not have a force-end-of-data operation. See your high-level language topic collection
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for further details.)</li>
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</ul>
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<p>Performing one of the methods mentioned previously synchronizes the access
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path and the data. However, the next change to the data in the file can turn
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the synchronization indicator off again. </p>
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<p>Note that each of the methods can be costly in terms of performance; therefore,
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use them with caution. Consider journaling access paths along with saving
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access paths or using SMAPP as the primary means of protecting access paths.</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="rbaforzahfpro.htm" title="Rebuilding a database access path might take as much as one minute for every 10 000 records. But some factors might affect the time estimate for rebuilding access paths.">Rebuild access paths</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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