58 lines
3.5 KiB
HTML
58 lines
3.5 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="Table size" />
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<meta name="abstract" content="The size of the tables that your application program accesses has a significant impact on the performance of the application program." />
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<meta name="description" content="The size of the tables that your application program accesses has a significant impact on the performance of the application program." />
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<meta name="DC.Relation" scheme="URI" content="rzaikdbdesign.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="tablesize" />
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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>Table size</title>
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</head>
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<body id="tablesize"><a name="tablesize"><!-- --></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">Table size</h1>
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<div><p>The size of the tables that your application program accesses has
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a significant impact on the performance of the application program.</p>
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<div class="section"><p>Consider the following: </p>
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<dl><dt class="dlterm">Large row length:</dt>
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<dd>For sequentially accessed tables that have a large row length because
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of many columns (100 or more), you may improve performance by dividing the
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tables into several smaller ones, or by creating a view. This assumes that
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your application is not accessing all of the columns. The main reason for
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the better performance is that I/O may be reduced because you will get more
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rows per page. Splitting the table will affect applications that access all
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of the columns because they will incur the overhead of joining the table back
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together again. You must decide where to split the table based on the nature
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of the application and frequency of access to various columns.</dd>
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<dt class="dlterm">Large number of rows:</dt>
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<dd>If a table has a large number of rows, construct your <span class="keyword">SQL</span> statements
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so that the <a href="rzaikoptimizer.htm#optimizer">Optimizer</a> uses an index
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to access the table. The <a href="indexes.htm#indexes">use of indexes</a> is
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very important for achieving the best possible performance.</dd>
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</dl>
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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="rzaikdbdesign.htm" title="Use the following topics to determine what tables you require in your database and to understand the relationship between those tables.">Database design</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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