81 lines
5.4 KiB
HTML
81 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="task" />
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<meta name="DC.Title" content="Manage the storage used by a data queue" />
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<meta name="abstract" content="Because smaller data queues have better performance than large ones, it's important to manage the size of the storage allocated to a data queue." />
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<meta name="description" content="Because smaller data queues have better performance than large ones, it's important to manage the size of the storage allocated to a data queue." />
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<meta name="DC.Relation" scheme="URI" content="compq.htm" />
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<meta name="DC.Relation" scheme="URI" content="../cl/crtdtaq.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<title>Manage the storage used by a data queue</title>
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</head>
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<body id="mangq"><a name="mangq"><!-- --></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">Manage the storage used by a data queue</h1>
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<div><p>Because smaller data queues have better performance than large
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ones, it's important to manage the size of the storage allocated to a data
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queue.</p>
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<div class="section"> <p>Each entry receives a storage allocation when sent to a data
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queue. The storage allocated will be the value that is specified for the maximum
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entry length of the data queue that was specified on the <span class="cmdname">Create Data
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Queue (CRTDTAQ)</span> command. When receiving an entry from a data queue,
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the data queue removes the entry, but it does not free the auxiliary storage.
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The system uses the auxiliary storage again when sending a new entry to the
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data queue. The queue grows larger when not receiving entries that are sent
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to the queue. Smaller queues that have not been extended past the initial
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number of entries have better performance. If a data queue has grown too large,
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delete the data queue by using the <span class="cmdname">Delete Data Queue (DLTDTAQ)</span> command.
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On completion of the data queue deletion, recreate the queue by using the <span class="cmdname">Create
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Data Queue (CRTDTAQ)</span> command.</p>
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<p>There is another way to manage
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the size of a data queue on Release V4R5M0 and beyond. This consists of using
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the SIZE and AUTORCL keywords on the <span class="cmdname">Create Data Queue (CRTDTAQ)</span> command.
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You can use the SIZE keyword to specify the maximum number of entries and
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the initial number of entries for the data queue. You can use
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the AUTORCL keyword for a queue that has been extended to indicate if the
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data queue should have storage automatically reclaimed when the queue is empty.
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The amount of storage that remains allocated to the queue equals the initial
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number of entries specified for the queue when it was created. If AUTORCL
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contains a value of *NO, which is the default, the system does not automatically
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reclaim storage from unused space. To reclaim the storage the data queue uses,
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you would need to delete and recreate it as described in the preceding paragraph.
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Auto reclaim may be expensive depending on the size of the queue, so the initial
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number of entries specified on the <span class="cmdname">Create Data Queue (CRTDTAQ)</span> command
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should be set to the largest typical number of entries that are expected to
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be on the data queue. If the initial number of entries is set too small, the
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system will execute the reclaim function more frequently.</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="qcomm.htm" title="Data queues are a type of system object that you can create, to which one HLL procedure or program can send data, and from which another HLL procedure or program can receive data.">Use data queues</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="compq.htm" title="This describes the differences between using data queues and using database files.">Comparisons with using database files as queues</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="../cl/crtdtaq.htm">Create Data Queue (CRTDTAQ) command</a></div>
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<div><a href="../cl/dltdtaq.htm">Delete Data Queue (DLTDTAQ) command</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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