84 lines
5.4 KiB
HTML
84 lines
5.4 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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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Controlling system wide parallel processing for queries" />
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<meta name="abstract" content="You can use the QQRYDEGREE system value to control parallel processing for a server." />
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<meta name="description" content="You can use the QQRYDEGREE system value to control parallel processing for a server." />
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<meta name="DC.subject" content="parallel processing, controlling, system wide (QQRYDEGREE) value" />
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<meta name="keywords" content="parallel processing, controlling, system wide (QQRYDEGREE) value" />
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<meta name="DC.Relation" scheme="URI" content="smp0001.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.Identifier" content="syswidepar" />
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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>Controlling system wide parallel processing for queries</title>
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</head>
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<body id="syswidepar"><a name="syswidepar"><!-- --></a>
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<img src="./delta.gif" alt="Start of change" /><!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Controlling system wide parallel processing for queries</h1>
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<div><p>You can use the QQRYDEGREE system value to control parallel processing
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for a server. </p>
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<div class="section"><div class="p">The current value of the system value can be displayed
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or modified using the following CL commands: <ul><li><a href="../cl/wrksysval.htm"><span class="cmdname">WRKSYSVAL</span></a> - <span class="cmdname">Work
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with System Value</span></li>
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<li><a href="../cl/chgsysval.htm"><span class="cmdname">CHGSYSVAL</span></a> - <span class="cmdname">Change
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System Value</span></li>
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<li><a href="../cl/dspsysval.htm"><span class="cmdname">DSPSYSVAL</span></a> - <span class="cmdname">Display
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System Value</span></li>
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<li><a href="../cl/rtvsysval.htm"><span class="cmdname">RTVSYSVAL</span></a> - <span class="cmdname">Retrieve
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System Value</span></li>
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</ul>
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</div>
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</div>
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<div class="section"><p>The special values for QQRYDEGREE control whether parallel processing
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is allowed by default for all jobs on the server. The possible values are:
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</p>
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<dl><dt class="dlterm"><span class="synph"><span class="kwd">*NONE</span></span></dt>
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<dd>No parallel processing is allowed for database query processing.</dd>
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<dt class="dlterm"><span class="synph"><span class="kwd">*IO</span></span></dt>
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<dd>I/O parallel processing is allowed for queries.</dd>
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<dt class="dlterm"><span class="synph"><span class="kwd">*OPTIMIZE</span></span></dt>
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<dd>The query optimizer can choose to use any number of tasks for either I/O
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or SMP parallel processing to process the queries. SMP parallel processing
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is used only if the <span class="keyword">DB2<sup>®</sup> UDB Symmetric Multiprocessing</span> feature
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is installed. The query optimizer chooses to use parallel processing to minimize
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elapsed time based on the job's share of the memory in the pool.</dd>
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<dt class="dlterm"><span class="synph"><span class="kwd">*MAX</span></span></dt>
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<dd>The query optimizer can choose to use either I/O or SMP parallel processing
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to process the query. SMP parallel processing can be used only if the <span class="keyword">DB2 UDB Symmetric Multiprocessing</span> feature is installed. The
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choices made by the query optimizer are similar to those made for parameter
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value *OPTIMIZE, except the optimizer assumes that all active memory in the
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pool can be used to process the query.</dd>
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</dl>
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</div>
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<div class="section"><p>The default value of the QQRYDEGREE system value is *NONE, so
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you must change the value if you want parallel query processing as the default
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for jobs run on the server.</p>
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</div>
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<div class="section"><p>Changing this system value affects all jobs that will be run or
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are currently running on the server whose DEGREE query attribute is *SYSVAL.
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However, queries that have already been started or queries using reusable
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ODPs are not affected.</p>
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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="smp0001.htm" title="There are two types of parallel processing available. The first is a parallel I/O that is available at no charge. The second is DB2 UDB Symmetric Multiprocessing, a feature that you can purchase. You can turn parallel processing on and off.">Control parallel processing for queries</a></div>
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</div>
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</div>
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<img src="./deltaend.gif" alt="End of change" /></body>
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</html>
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