96 lines
7.1 KiB
HTML
96 lines
7.1 KiB
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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="concept" />
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<meta name="DC.Title" content="Objects processed in parallel" />
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<meta name="abstract" content="The DB2 UDB Symmetric Multiprocessing feature provides the optimizer with additional methods for retrieving data that include parallel processing. Symmetrical multiprocessing (SMP) is a form of parallelism achieved on a single server where multiple (CPU and I/O) processors that share memory and disk resource work simultaneously toward achieving a single end result." />
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<meta name="description" content="The DB2 UDB Symmetric Multiprocessing feature provides the optimizer with additional methods for retrieving data that include parallel processing. Symmetrical multiprocessing (SMP) is a form of parallelism achieved on a single server where multiple (CPU and I/O) processors that share memory and disk resource work simultaneously toward achieving a single end result." />
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<meta name="DC.subject" content="definitions, symmetrical multiprocessing" />
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<meta name="keywords" content="definitions, symmetrical multiprocessing" />
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<meta name="DC.Relation" scheme="URI" content="rzajqdta.htm" />
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<meta name="DC.Relation" scheme="URI" content="../db2/rbafzsetdegree.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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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>Objects processed in parallel</title>
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</head>
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<body id="rzajq1parallel"><a name="rzajq1parallel"><!-- --></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">Objects processed in parallel</h1>
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<div><p>The <span class="keyword">DB2<sup>®</sup> UDB Symmetric Multiprocessing</span> feature
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provides the optimizer with additional methods for retrieving data that include
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parallel processing. Symmetrical multiprocessing (SMP) is a form of parallelism
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achieved on a single server where multiple (CPU and I/O) processors that share
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memory and disk resource work simultaneously toward achieving a single end
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result.</p>
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<p>This parallel processing means that the database manager can have more
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than one (or all) of the server processors working on a single query simultaneously.
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The performance of a CPU bound query can be significantly improved with this
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feature on multiple-processor servers by distributing the processor load across
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more than one processor.</p>
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<p>The tables above indicate what data access method are enabled to take advantage
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of the DB2 UDB
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Symmetric Multiprocessing feature. An important thing to note, however, is
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that the parallel implementation differs for both the SQL Query Engine and
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the Classic Query Engine. </p>
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<div class="section"><img src="./delta.gif" alt="Start of change" /><h4 class="sectiontitle">Processing requirements</h4><p>Parallelism requires
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that SMP parallel processing must be enabled by one of the following methods:</p>
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<ul><li>System value QQRYDEGREE</li>
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<li>Query option file</li>
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<li>DEGREE parameter on the <span class="cmdname">Change Query Attributes (CHGQRYA)</span> command</li>
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<li>SQL SET CURRENT DEGREE statement</li>
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</ul>
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<p>Once parallelism has been enabled, a set of database system tasks
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or threads is created at server startup for use by the database manager.
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The database manager uses the tasks to process and retrieve data from different
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disk devices. Since these tasks can be run on multiple processors simultaneously,
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the elapsed time of a query can be reduced. Even though much of the I/O and
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CPU processing of a parallel query is done by the tasks, the accounting of
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the I/O and CPU resources used are transferred to the application job. The
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summarized I/O and CPU resources for this type of application continue to
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be accurately displayed by the <span class="cmdname">Work with Active Jobs (WRKACTJOB)</span> command.</p>
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<p>The
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job should be run in a shared storage pool with the *CALC paging option, as
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this will cause more efficient use of active memory. </p>
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<img src="./deltaend.gif" alt="End of change" /></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="rzajqdta.htm" title="Data access methods are used to process queries and access data.">Data access on DB2 UDB for iSeries: data access paths and methods</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="c23nl.htm" title="DB2 Universal Database for iSeries provides a nested loop join method. For this method, the processing of the tables in the join are ordered. This order is called the join order. The first table in the final join order is called the primary table. The other tables are called secondary tables. Each join table position is called a dial.">Nested loop join implementation</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="cqa.htm" title="You can modify different types of attributes of the queries that you will execute during a certain job with the Change Query Attributes (CHGQRYA) CL command, or by using the iSeries Navigator Change Query Attributes interface.">Change the attributes of your queries with the Change Query Attributes (CHGQRYA) command</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="../db2/rbafzsetdegree.htm">SET CURRENT DEGREE statement</a></div>
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<div><a href="../rzakz/rzakzqqrydegree.htm">Parallel processing for queries and indexes system value</a></div>
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<div><a href="../rzahx/rzahxtuneautotune.htm">Automatically tune performance</a></div>
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<div><a href="../cl/wrkactjob.htm">Work with Active Jobs (WRKACTJOB) command</a></div>
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<div><a href="../cl/chgqrya.htm">Change Query Attributes (CHGQRYA) 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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