73 lines
4.0 KiB
HTML
73 lines
4.0 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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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="security" content="public" />
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<meta name="Robots" content="index,follow" />
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Example: Query tool B" />
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<meta name="abstract" content="This example illustrates using one allocation statement for the entire call." />
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<meta name="description" content="This example illustrates using one allocation statement for the entire call." />
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<meta name="DC.Relation" scheme="URI" content="rzaiktoolsbadperf.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1999, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1999, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="odbcquerytoolb" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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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>Example: Query tool B</title>
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</head>
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<body id="odbcquerytoolb"><a name="odbcquerytoolb"><!-- --></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">Example: Query tool B</h1>
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<div><p>This example illustrates using one allocation statement for the
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entire call.</p>
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<div class="section"><p>Query tool B allows you to update a spreadsheet of rows and then
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send the updates to the database. It makes the following ODBC calls: </p>
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<pre> FOR every_row_updated DO
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SQLAllocHandle(SQL_HANDLE_STMT)
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SQLExecDirect("UPDATE...SET COLn='literal'...WHERE COLn='oldval'...")
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SQLFreeHandle( SQL_HANDLE_STMT )
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END LOOP</pre>
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</div>
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<div class="section"><p>The first thing to note is that the tool performs a statement
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allocation-and-drop for every row. Only one allocate statement is needed.
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This change would save the overhead of creating and destroying a statement
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handle for every operation. Another performance concern is the use of <span class="keyword">SQL</span> with literals instead of with
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parameter markers. The <strong>SQLExecDirect()</strong> call causes an <strong>SQLPrepare</strong> and <strong>SQLExecute</strong> every
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time. A faster way to perform this operation would be as follows: </p>
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<pre> SQLAllocHandle(SQL_HANDLE_STMT)
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SQLPrepare("UPDATE...SET COL1=?...WHERE COL1=?...")
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SQLBindParameter( new_column_buffers )
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SQLBindParameter( old_column_buffers )
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FOR every_row_updated DO
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...move each rows data into the SQLBindParameter buffers
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SQLExecute()
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SQLFreeHandle( SQL_HANDLE_STMT )
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END LOOP</pre>
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</div>
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<div class="section"><p>These sets of ODBC calls will outperform the original set by a
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large factor when you are using the <span class="keyword">iSeries™ Access for Windows<sup>®</sup></span> ODBC
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driver. The server CPU utilization will decrease to 10 percent of what it
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was, which pushes the scaling threshold out a lot farther.</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="rzaiktoolsbadperf.htm" title="The following examples demonstrate performance problems that are associated with writing SQL and ODBC calls that do NOT take advantage of a unique feature of a particular ODBC driver or the server database management system.">Examples: Common tool behaviors that degrade ODBC performance</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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