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HTML
127 lines
8.0 KiB
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Performance system values: Thread affinity" />
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<meta name="abstract" content="Specifies whether or not secondary threads will have affinity to the same group of processors and memory as the initial thread. (QTHDRSCAFN)" />
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<meta name="description" content="Specifies whether or not secondary threads will have affinity to the same group of processors and memory as the initial thread. (QTHDRSCAFN)" />
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<title>Performance system values: Thread affinity</title>
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</head>
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<body id="rzakzqthdrscafn"><a name="rzakzqthdrscafn"><!-- --></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: Thread affinity</h1>
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<div><p>Specifies whether or not secondary threads will have affinity to
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the same group of processors and memory as the initial thread. (QTHDRSCAFN)</p>
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<p><span class="uicontrol">Thread affinity</span>, also known as <span class="uicontrol">QTHDRSCAFN</span>,
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is a member of the performance category of i5/OS™ system values. You can use this system
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value to specify whether secondary threads are grouped with the initial thread
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(thread level) or not. It also specifies the degree to which the system tries
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to maintain the affinity between threads and the subset of resources they
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are assigned to (level of affinity). 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">Affinity</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 ">Thread affinity: <span class="uicontrol">Secondary threads do not use same processors
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and memory as initial thread.</span> Level of affinity: <span class="uicontrol">Threads
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use any resource.</span></td>
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</tr>
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<tr><th valign="top" class="firstcol" id="d0e68" headers="d0e31 ">Changes take effect</th>
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<td valign="top" headers="d0e68 d0e31 ">Immediately, but not for jobs already started.</td>
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</tr>
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<tr><th valign="top" class="firstcol" id="d0e73" headers="d0e31 ">Lockable</th>
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<td valign="top" headers="d0e73 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 secondary threads will have affinity to the same group of processors
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and memory as the initial thread or not. It also specifies the degree to which
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the system tries to maintain the affinity between threads and the subset of
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system resources they are assigned to.</p>
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<p>A change to this system value
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takes effect immediately for all jobs that become active after the change,
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but only if they retrieve their affinity values from the system value. Jobs
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and threads that are currently active will continue to run with the affinity
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values they were started with. New jobs and threads that get their affinity
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values from jobs that are currently active, (for example, batch immediate
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jobs or secondary threads that inherit attributes from the initial thread),
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will continue to use the values stored in the initiating job or thread, rather
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than the current system value.</p>
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<p>In addition, use the automatically adjust
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thread resources (QTHDRSCADJ) system value to distribute the use of system
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resources.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Thread affinity</h4><p>Specifies whether or not secondary
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threads are grouped with the initial thread. Select one of the following:</p>
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<dl><dt class="dlterm">Secondary threads use same processors and memory as initiating thread
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(*GROUP)</dt>
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<dd>Indicates that secondary threads have a preference for the same group
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of processors and memory as the initial thread. Multi-threaded workloads that
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share data between the threads within a job may perform better when using
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this option.</dd>
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<dt class="dlterm">Secondary threads do not use same processors and memory as initiating
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thread (*NOGROUP)</dt>
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<dd>Indicates that secondary threads do not have a preference for the same
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group of processors and memory as the initial thread. Workloads that use the
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full processing power of a system may perform better when using this option.</dd>
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</dl>
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</div>
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<div class="section"><h4 class="sectiontitle">Level of affinity</h4><p>Specifies the degree to which
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the threads try to use the subset of system resources that they have a preference
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for. Select one of the following:</p>
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<dl><dt class="dlterm">Threads only use resources they have affinity to (*HIGH)</dt>
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<dd>Threads will only use the subset of system resources they have affinity
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to, and will wait until they become available.</dd>
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<dt class="dlterm">Threads use any resource (*NORMAL)</dt>
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<dd>Threads will use any processor or memory in the system if the resources
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they have affinity to are not readily available.</dd>
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</dl>
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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><a href="rzakzqthdrscadj.htm" title="Specifies whether or not the system should dynamically make adjustments to the affinity of threads currently running on the system. (QTHDRSCADJ)">Performance system values: Automatically adjust thread resources</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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</html>
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