157 lines
8.3 KiB
HTML
157 lines
8.3 KiB
HTML
<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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<html xmlns="http://www.w3.org/1999/xhtml" lang="en-US" xml:lang="en-us">
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<meta name="dc.date" scheme="iso8601" content="2005-09-19" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="keywords" content="SET CURRENT DEGREE statement, SET CURRENT DEGREE,
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SQL statements" />
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<title>SET CURRENT DEGREE</title>
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<link rel="stylesheet" type="text/css" href="ic.css" />
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</head>
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<body>
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<a id="Top_Of_Page" name="Top_Of_Page"></a><!-- Java sync-link -->
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<script language = "Javascript" src = "../rzahg/synch.js" type="text/javascript"></script>
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<a name="setdegree"></a>
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<h2 id="setdegree"><a href="rbafzmst02.htm#ToC_1290">SET CURRENT DEGREE</a></h2><a id="idx3128" name="idx3128"></a><a id="idx3129" name="idx3129"></a>
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<p>The SET CURRENT DEGREE statement assigns a value to the CURRENT DEGREE
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special register.</p>
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<a name="wq1743"></a>
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<h3 id="wq1743"><a href="rbafzmst02.htm#ToC_1291">Invocation</a></h3>
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<p>This statement can be embedded in an application program or
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issued interactively. It is an executable statement that can be dynamically
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prepared. It must not be specified in REXX.</p>
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<a name="wq1744"></a>
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<h3 id="wq1744"><a href="rbafzmst02.htm#ToC_1292">Authorization</a></h3>
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<p>The privileges held by the authorization ID of the statement must include
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the system authority of *JOBCTL.</p>
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<a name="wq1745"></a>
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<h3 id="wq1745"><a href="rbafzmst02.htm#ToC_1293">Syntax</a></h3>
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<a href="rbafzsetdegree.htm#synsetdegree"><img src="c.gif" alt="Click to skip syntax diagram" /></a>
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<pre class="cgraphic"><span><img src="c.gif" alt="Read syntax diagram" longdesc="rbafzmstsyn380.htm"
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border="0" /></span><a href="#skipsyn-379"><img src="c.gif" alt="Skip visual syntax diagram"
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border="0" /></a> .-=-.
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>>-SET--CURRENT DEGREE--+---+--+-<span class="italic">string-constant</span>-+-------------><
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+-<span class="italic">variable</span>--------+
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'-DEFAULT---------'
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</pre>
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<a name="skipsyn-379" id="skipsyn-379"></a>
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<a name="synsetdegree"></a>
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<h3 id="synsetdegree"><a href="rbafzmst02.htm#ToC_1294">Description</a></h3>
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<p>The value of CURRENT DEGREE is replaced by the value of the
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string constant or variable. The value must be a string with an actual length
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that is not greater than 5 after trimming any leading and trailing blanks.
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The value must be one of the following:</p>
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<dl class="parml">
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<dt class="bold">1</dt>
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<dd>No parallel processing is allowed.
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</dd>
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<dt class="bold"><var class="pv">2 through 32767</var></dt>
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<dd>Specifies the degree of parallelism that will be used.
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</dd>
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<dt class="bold">ANY</dt>
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<dd>Specifies that the database manager can choose to use any number of tasks for either
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I/O or SMP parallel processing.
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<p>Use of parallel processing and the number
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of tasks used is determined based on the number of processors available in
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the system, this job's share of the amount of active memory available in the
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pool in which the job is run, and whether the expected elapsed time for the
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operation is limited by CPU processing or I/O resources. The database manager chooses
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an implementation that minimizes elapsed time based on the job's share of
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the memory in the pool.</p>
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</dd>
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<dt class="bold">NONE</dt>
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<dd>No parallel processing is allowed.
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</dd>
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<dt class="bold">MAX</dt>
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<dd>The database manager can choose to use any number of tasks for either I/O or SMP
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parallel processing. MAX is similar to ANY except the database manager assumes that all
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active memory in the pool can be used.
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</dd>
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<dt class="bold">IO</dt>
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<dd>Any number of tasks can be used when the database manager chooses to use I/O parallel
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processing for queries. SMP is not allowed.
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</dd>
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</dl>
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<dl class="parml">
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<dt class="bold"><var class="pv">variable</var></dt>
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<dd>Specifies a variable that contains the value for the CURRENT DEGREE.
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<p>The variable: </p>
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<ul>
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<li>Must be a CHAR, VARCHAR, UTF-16 or UCS-2 GRAPHIC, or UTF-16
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or UCS-2 VARGRAPHIC variable. The actual length of the contents of the <var class="pv">variable</var> must not be greater than 5 after trimming any leading and trailing
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blanks.</li>
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<li>Must not be the null value.</li>
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<li>All characters are case-sensitive and are not converted to uppercase characters.</li></ul>
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</dd>
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<dt class="bold"><var class="pv">string-constant</var></dt>
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<dd>A character constant. The length of the constant must not exceed 5.
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</dd>
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<dt class="bold">DEFAULT</dt>
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<dd>If the PARALLEL_DEGREE parameter in a current query options
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file (QAQQINI) is specified, the CURRENT DEGREE will be reset to the PARALLEL_DEGREE.
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Otherwise, the CURRENT DEGREE will be reset from the degree specified by the
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QQRYDEGREE system value.
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</dd>
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</dl>
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<a name="wq1746"></a>
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<h3 id="wq1746"><a href="rbafzmst02.htm#ToC_1295">Notes</a></h3>
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<p><span class="bold">Transaction considerations:</span> The SET CURRENT DEGREE
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statement is not a commitable operation. ROLLBACK has no effect on CURRENT
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DEGREE.</p>
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<p><span class="bold">Initial current degree:</span> The initial value of CURRENT
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DEGREE is equal to the parallelism degree in effect from the CHGQRYA CL command,
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PARALLEL_DEGREE parameter in the current query options file (QAQQINI), or
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the QQRYDEGREE system value.</p>
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<p><span class="bold">Parallelism degree precedence:</span> The parallelism degree
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can be controlled in several ways. The actual parallelism degree used is determined
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as follows:</p>
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<ul>
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<li>If a SET CURRENT DEGREE statement or a CHGQRYA CL command with a DEGREE
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keyword has been executed, the parallelism degree specified by the most recent
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of either is the value of CURRENT DEGREE.</li>
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<li>If neither a SET CURRENT DEGREE statement nor a CHGQRYA CL command with
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a DEGREE keyword has been executed,
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<ul>
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<li>If a current query options file (QAQQINI) with a PARALLEL_DEGREE parameter
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has been specified, the parallelism degree specified by the QAQQINI file is
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the value of CURRENT DEGREE.</li>
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<li>Otherwise, the parallelism degree specified by the QQRYDEGREE system value
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is the value of CURRENT DEGREE.</li></ul></li></ul><p class="indatacontent">For more information, see <a href="../rzajq/rzajqkickoff.htm">Database Performance and
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Query Optimization</a>.</p>
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<p><span class="bold">Current degree scope:</span> The scope of CURRENT DEGREE
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is the job.</p>
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<p><span class="bold">Parallel limitations:</span> If the DB2® UDB Symmetric
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Multiprocessing feature is not installed, a warning is returned and parallelism
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is not used.</p>
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<p>Some SQL statements cannot use parallelism.</p>
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<a name="wq1747"></a>
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<h3 id="wq1747"><a href="rbafzmst02.htm#ToC_1296">Example</a></h3>
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<p><span class="italic">Example 1:</span> The following statement sets the CURRENT
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DEGREE to inhibit parallelism.</p>
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<pre class="xmp"> <span class="bold">SET CURRENT DEGREE =</span> '1' </pre>
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<p><span class="italic">Example 2:</span> The following statement sets the CURRENT
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DEGREE to allow parallelism.</p>
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<pre class="xmp"> <span class="bold">SET CURRENT DEGREE =</span> 'ANY' </pre>
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<hr /><br />
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