114 lines
6.9 KiB
HTML
114 lines
6.9 KiB
HTML
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<meta name="DC.Title" content="Performance system values: Parallel processing for queries and indexes" />
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<meta name="abstract" content="Specifies whether to use parallel processing and what to use it for. (QQRYDEGREE)" />
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<title>Performance system values: Parallel processing for queries and indexes</title>
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<body id="rzakzqqrydegree"><a name="rzakzqqrydegree"><!-- --></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">Performance system values: Parallel processing for queries and indexes</h1>
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<div><p>Specifies whether to use parallel processing and what to use it
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for. (QQRYDEGREE)</p>
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<p><span class="uicontrol">Parallel processing for queries and indexes</span>, also
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known as <span class="uicontrol">QQRYDEGREE</span>, is a member of the performance
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category of i5/OS™ system
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values. You can use this system value to specify whether to use parallel processing
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and what to use it for. To learn more, keep reading.</p>
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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" valign="top" class="firstcol" id="d0e31">Quick reference</th>
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</tr>
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</thead>
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<tbody><tr><th valign="top" class="firstcol" id="d0e35" headers="d0e31 ">Location</th>
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<td valign="top" headers="d0e35 d0e31 ">In iSeries™ Navigator,
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select your system, <span class="menucascade"><span class="uicontrol"></span> > <span class="uicontrol">Configuration
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and Service</span> > <span class="uicontrol">System Values</span> > <span class="uicontrol">Performance</span> > <span class="uicontrol">Database</span></span></td>
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</tr>
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<tr><th valign="top" class="firstcol" id="d0e53" headers="d0e31 ">Special authority</th>
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<td valign="top" headers="d0e53 d0e31 ">All object (*ALLOBJ) and security administrator (*SECADM)</td>
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</tr>
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<tr><th valign="top" class="firstcol" id="d0e58" headers="d0e31 ">Default value</th>
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<td valign="top" headers="d0e58 d0e31 ">Do not allow parallel processing</td>
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</tr>
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<tr><th valign="top" class="firstcol" id="d0e63" headers="d0e31 ">Changes take effect</th>
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<td valign="top" headers="d0e63 d0e31 ">Immediately</td>
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</tr>
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<tr><th valign="top" class="firstcol" id="d0e68" headers="d0e31 ">Lockable</th>
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<td valign="top" headers="d0e68 d0e31 ">No</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 class="section"><h4 class="sectiontitle">What can I do with this system value?</h4><p>Specifies
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whether to allow parallel processing and whether the type of parallel processing
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is input/output (I/O) parallel processing or symmetric multiprocessing (SMP).
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For I/O parallel processing, the database manager can use multiple tasks for
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input/output auxiliary storage processing for each query. Processing for the
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central processing unit (CPU) is still done serially. For symmetric multiprocessing,
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the CPU and I/O processing are assigned to tasks that run the query in parallel.
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Actual CPU parallelism requires a system with multiple processors. SMP parallelism
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is used only if the system feature DB2<sup>®</sup> Symmetric Multiprocessing for i5/OS is installed.</p>
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<div class="note"><span class="notetitle">Example:</span> To determine what parts you need to buy for
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your company, you run a query of inventory from a database. By running the
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query, you determine which parts are sold out so you can replace them with
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new parts. The query takes a long time to complete because the processors
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cannot run at the same time. To increase the system performance, you should
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allow parallel processing. This allows different processors to run at the
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same time to perform the query much faster.</div>
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<p>The following are possible
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options:</p>
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<ul><li><span class="uicontrol">Do not allow parallel processing (*NONE)</span> <p>No
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parallel processing is allowed for database query processing.</p>
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</li>
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<li><span class="uicontrol">Use multiple processes for input/output (*IO)</span> <p>The
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database query optimizer can use any number of tasks for I/O parallel processing
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for queries. SMP parallel processing is not allowed.</p>
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</li>
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<li><span class="uicontrol">Use multiple processes for input/output, queries, and indexes
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(*OPTIMIZE)</span> <p>The query optimizer can use any number of tasks
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for either I/O or SMP parallel processing for queries. If you select to use
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multiple processes for input/output, queries, and indexes, you can also select
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to <span class="uicontrol">Use all active memory in memory pool (*MAX)</span>. Using
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all active memory allows the query optimizer to choose an access plan that
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might consume more of the system resources, but would provide faster run time
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for a given query.</p>
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</li>
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</ul>
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</div>
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<div class="section"><h4 class="sectiontitle">Where can I get more information about this system value?</h4><p>To
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learn more, go to the performance system values overview topic. If you are
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looking for a specific system value or category of system values, try using
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the i5/OS system
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value finder.</p>
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</div>
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</div>
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<div><div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rzakzperformanceoverview.htm" title="Use i5/OS performance system values to view and change priority, performance adjustments, and processing values for the system.">System values: Performance overview</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="rzakzfinder.htm">System value finder</a></div>
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</div>
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</div>
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</body>
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