61 lines
3.5 KiB
HTML
61 lines
3.5 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 http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="SQL4023 - Parallel table prefetch used" />
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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="sql4023" />
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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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<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>SQL4023 - Parallel table prefetch used</title>
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</head>
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<body id="sql4023"><a name="sql4023"><!-- --></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">SQL4023 - Parallel table prefetch used</h1>
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<div>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><thead align="left"><tr><th colspan="2" align="center" valign="middle" id="d0e16">SQL4023</th>
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</tr>
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</thead>
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<tbody><tr valign="middle"><td valign="middle" width="26.02040816326531%" headers="d0e16 ">Message Text:</td>
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<td valign="middle" width="73.9795918367347%" headers="d0e16 ">Parallel table prefetch used</td>
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</tr>
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<tr valign="middle"><td valign="middle" width="26.02040816326531%" headers="d0e16 ">Cause Text:</td>
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<td valign="middle" width="73.9795918367347%" headers="d0e16 ">The query optimizer chose to use a parallel prefetch access method
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to reduce the processing time required for the table scan.</td>
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</tr>
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<tr valign="middle"><td valign="middle" width="26.02040816326531%" headers="d0e16 ">Recovery Text:</td>
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<td valign="middle" width="73.9795918367347%" headers="d0e16 ">Parallel prefetch can improve the performance of queries. Even though
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the access plan was created to use parallel prefetch, the system will actually
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run the query only if the following are true: <ul><li>The query attribute degree was specified with an option of *IO or *ANY
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for the application process.</li>
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<li>There is enough main storage available to cache the data being retrieved
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by multiple I/O streams. Normally, 5 megabytes would be a minimum. Increasing
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the size of the shared pool may improve performance.</li>
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</ul>
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For more information about parallel table prefetch, refer to <a href="rzajqdta.htm#rzajqdta">Data access on DB2 UDB for iSeries: data access paths and methods</a></td>
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</tr>
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</tbody>
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</table>
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</div>
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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="prtsqlinfmsg.htm" title="The following are the messages returned from PRTSQLINF.">PRTSQLINF message reference</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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