111 lines
8.4 KiB
HTML
111 lines
8.4 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<meta name="DC.Title" content="Effects of precompile options on database performance" />
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<meta name="abstract" content="Several precompile options are available for creating SQL programs with improved performance. They are only options because using them may impact the function of the application. For this reason, the default value for these parameters is the value that will ensure successful migration of applications from prior releases. However, you can improve performance by specifying other options." />
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<title>Effects of precompile options on database performance</title>
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</head>
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<body id="precompileopts"><a name="precompileopts"><!-- --></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">Effects of precompile options on database performance</h1>
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<div><p>Several precompile options are available for creating SQL programs
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with improved performance. They are only options because using them may impact
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the function of the application. For this reason, the default value for these
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parameters is the value that will ensure successful migration of applications
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from prior releases. However, you can improve performance by specifying other
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options.</p>
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<div class="section"><p>The following table shows these precompile options and their performance
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impacts.</p>
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</div>
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<div class="section"><p>Some of these options may be suitable for most of your applications.
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Use the command <span class="cmdname">CRTDUPOBJ</span> to create a copy of the SQL <span class="cmdname">CRTSQLxxx</span>
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command. and the <span class="cmdname">CHGCMDDFT</span> command to customize the optimal
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values for the precompile parameters. The <span class="cmdname">DSPPGM</span>, <span class="cmdname">DSPSRVPGM</span>, <span class="cmdname">DSPMOD</span>,
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or <span class="cmdname">PRTSQLINF</span> commands can be used to show the precompile
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options that are used for an existing program object.</p>
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</div>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" width="100%" frame="hsides" border="1" rules="all"><thead align="left"><tr><th align="left" valign="bottom" width="25%" id="d0e69">Precompile Option</th>
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<th align="left" valign="bottom" width="25%" id="d0e71">Optimal Value</th>
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<th align="left" valign="bottom" width="25%" id="d0e73">Improvements</th>
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<th align="left" valign="bottom" width="25%" id="d0e75">Considerations</th>
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</tr>
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</thead>
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<tbody><tr><td align="left" valign="top" width="25%" headers="d0e69 ">ALWCPYDTA</td>
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<td align="left" valign="top" width="25%" headers="d0e71 ">*OPTIMIZE (the default)</td>
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<td align="left" valign="top" width="25%" headers="d0e73 ">Queries where the ordering or grouping criteria
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conflicts with the selection criteria.</td>
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<td align="left" valign="top" width="25%" headers="d0e75 ">A copy of the data may be made when the query
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is opened.</td>
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</tr>
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<tr><td align="left" valign="top" width="25%" headers="d0e69 ">ALWBLK</td>
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<td align="left" valign="top" width="25%" headers="d0e71 ">*ALLREAD (the default)</td>
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<td align="left" valign="top" width="25%" headers="d0e73 ">Additional read-only cursors use blocking.</td>
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<td align="left" valign="top" width="25%" headers="d0e75 ">ROLLBACK HOLD may not change the position
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of a read-only cursor. Dynamic processing of positioned updates or deletes
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might fail.</td>
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</tr>
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<tr><td align="left" valign="top" width="25%" headers="d0e69 ">CLOSQLCSR</td>
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<td align="left" valign="top" width="25%" headers="d0e71 ">*ENDJOB, *ENDSQL, or *ENDACTGRP</td>
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<td align="left" valign="top" width="25%" headers="d0e73 ">Cursor position can be retained across program
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invocations.</td>
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<td align="left" valign="top" width="25%" headers="d0e75 ">Implicit closing of SQL cursor is not done
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when the program invocation ends.</td>
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</tr>
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<tr><td align="left" valign="top" width="25%" headers="d0e69 ">DLYPRP</td>
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<td align="left" valign="top" width="25%" headers="d0e71 ">*YES</td>
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<td align="left" valign="top" width="25%" headers="d0e73 ">Programs using SQL PREPARE statements may
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run faster.</td>
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<td align="left" valign="top" width="25%" headers="d0e75 ">Complete validation of the prepared statement
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is delayed until the statement is run or opened.</td>
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</tr>
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<tr><td align="left" valign="top" width="25%" headers="d0e69 ">TGTRLS</td>
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<td align="left" valign="top" width="25%" headers="d0e71 ">*CURRENT (the default)</td>
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<td align="left" valign="top" width="25%" headers="d0e73 ">The precompiler can generate code that will
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take advantage of performance enhancements available in the current release.</td>
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<td align="left" valign="top" width="25%" headers="d0e75 ">The program object cannot be used on a server
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from a previous release.</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>
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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="genconsid.htm" title="As you code your applications, there are some general tips that can help you optimize performance.">General DB2 UDB for iSeries performance considerations</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="ipuc.htm" title="Some complex queries can perform better by using a sort or hashing method to evaluate the query instead of using or creating an index.">Effects of the ALWCPYDTA parameter on database performance</a></div>
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<div><a href="ipbc.htm" title="To improve performance, the SQL runtime attempts to retrieve and insert rows from the database manager a block at a time whenever possible.">Control database manager blocking</a></div>
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<div><a href="retcurs.htm" title="For non-ILE program calls, the close SQL cursor (CLOSQLCSR) parameter allows you to specify the scope of the following:">Retaining cursor positions for non-ILE program calls</a></div>
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<div><a href="ipps.htm" title="The processing which occurs when an SQL PREPARE statement is run is similar to the processing which occurs during precompile processing.">Eliminate redundant validation with SQL PREPARE statements</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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