63 lines
4.4 KiB
HTML
63 lines
4.4 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="copyright" content="(C) Copyright IBM Corporation 2005" />
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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="Details of the COMPRESS(*NO) parameter and the CPYF command" />
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<meta name="abstract" content="The COMPRESS(*NO) parameter allows the system to copy more quickly because records are transferred in blocks, but this is not always true. Typically, the COMPRESS(*NO) function does not significantly affect performance." />
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<meta name="description" content="The COMPRESS(*NO) parameter allows the system to copy more quickly because records are transferred in blocks, but this is not always true. Typically, the COMPRESS(*NO) function does not significantly affect performance." />
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<meta name="DC.Relation" scheme="URI" content="rbal3copydelrec.htm" />
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<meta name="DC.Identifier" content="rbal3details" />
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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>Details of the COMPRESS(*NO) parameter and the CPYF command</title>
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</head>
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<body id="rbal3details"><a name="rbal3details"><!-- --></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">Details of the COMPRESS(*NO) parameter and the CPYF command</h1>
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<div><p>The COMPRESS(*NO) parameter allows the system to copy more quickly
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because records are transferred in blocks, but this is <em>not always</em> true.
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Typically, the COMPRESS(*NO) function does not significantly affect performance.</p>
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<div class="p"><img src="./delta.gif" alt="Start of change" />Before you specify the COMPRESS(*NO) parameter, be aware
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that when you use the COMPRESS(*NO) parameter, the system takes the following
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actions:<ul><li>Before the records are copied, the system invalidates any key access paths
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that use the to-file member.</li>
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<li>After the copy operation is complete, the system rebuilds
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the access paths.</li>
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</ul>
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The runtime and resource that are required to rebuild the keyed access
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paths might outweigh the performance benefit that is gained by copying deleted
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records.<img src="./deltaend.gif" alt="End of change" /></div>
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<p>If you do not specify the COMPRESS(*NO) parameter, the system might still
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use the internal functions to perform the copy, but the choice of how the
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copy is performed is based on the number of records in the from-file and to-file
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members before the copy, and the number of keyed access paths over the to-file
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member.</p>
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<p>If you specify the MBROPT(*REPLACE) parameter, all keyed access paths over
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the to-file member must be invalidated and rebuilt, so specifying COMPRESS(*NO)
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does not cause any additional overhead for rebuilding access paths.</p>
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<p>If the from-file is a keyed physical file and neither a FROMRCD nor TORCD
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relative record number value is specified on the copy commands to force the
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file to be processed in arrival sequence, COMPRESS(*NO) has no meaning because
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a keyed access path never contains any deleted records.</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="rbal3copydelrec.htm" title="You might want to copy deleted records to preserve the relative record numbers of records that are copied from the from-file. You can copy both deleted and undeleted records from one physical file member to another by specifying the COMPRESS(*NO) parameter on a copy command.">Copy deleted records (COMPRESS parameter)</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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