75 lines
5.1 KiB
HTML
75 lines
5.1 KiB
HTML
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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.Title" content="Temporary buffer" />
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<meta name="abstract" content="The temporary buffer is a temporary object that is used to help facilitate operations such as parallelism. It is an unsorted data structure that is used to store intermediate rows of a query. The main difference between a temporary buffer and a temporary list is that the buffer does not need to be fully populated in order to allow its results to be processed." />
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<meta name="DC.subject" content="definitions, temporary buffer access method, temporary buffer, scan access method, access method" />
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<meta name="keywords" content="definitions, temporary buffer access method, temporary buffer, scan access method, access method" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<title>Temporary buffer</title>
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</head>
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<body id="rzajqtempbuff"><a name="rzajqtempbuff"><!-- --></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">Temporary buffer</h1>
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<div><p>The temporary buffer is a temporary object that is used to help
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facilitate operations such as parallelism. It is an unsorted data structure
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that is used to store intermediate rows of a query. The main difference between
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a temporary buffer and a temporary list is that the buffer does not need to
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be fully populated in order to allow its results to be processed.</p>
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<div class="section"><p>The temporary buffer acts as a serialization point between parallel
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and non-parallel portions of a query. The operations used to populate the
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buffer cannot be performed in parallel, whereas the operations that fetch
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rows from the buffer can be performed in parallel. The temporary buffer is
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required for the SQL Query Engine because the index scan and index probe operations
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are not considered to be SMP parallel enabled for this engine. Unlike the
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Classic Query Engine, which will perform these index operations in parallel,
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the SQL Query Engine will not subdivide the work necessary within the index
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operation to take full advantage of parallel processing. The buffer is used
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to allow a query to be processed under parallelism by serializing access to
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the index operations, while allowing any remaining work within the query to
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be processed in parallel.</p>
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</div>
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<div class="section"><p>A temporary buffer is an internal data structure and can only
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be created by the database manager.</p>
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</div>
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<div class="section"><p>Visual explain icon:</p>
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</div>
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<div class="section"><p><img src="rzajq537.gif" alt="Temporary buffer icon" /></p>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rzajqbuffscan.htm">Buffer scan</a></strong><br />
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The buffer scan operation is used when a query is processed using DB2<sup>®</sup> UDB
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Symmetric Multiprocessing, yet a portion of the query is not enabled to be
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processed under parallelism. The buffer scan acts as a gateway to control
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access to rows between the parallel enabled portions of the query and the
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non-parallel portions.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzajqtempobj.htm" title="Temporary objects are created by the optimizer in order to process a query. In general, these temporary objects are internal objects and cannot be accessed by a user.">Temporary objects and access methods</a></div>
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</div>
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</div>
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</body>
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