120 lines
6.1 KiB
HTML
120 lines
6.1 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="Examples: Database file sizes" />
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<meta name="DC.Relation" scheme="URI" content="rbafoappmax.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="rbafoappmaxex1" />
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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>Examples: Database file sizes</title>
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</head>
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<body id="rbafoappmaxex1"><a name="rbafoappmaxex1"><!-- --></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">Examples: Database file sizes</h1>
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<div><div class="section"><div class="p">A *MAX1TB (4-byte) access path with 120 byte keys and 500 000
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records TotalIndexSize has a TotalIndexSize in bytes as follows: <pre>a = (LimbPageUtilization - LogicalPageHeaderSize) *
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(LogicalPageHeaderSize - LeafPageUtilization - 2 * NodeSize)
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= (6144 - 64) *
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(64 - 6554 - 2 * 4)
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= 6080 * -6498
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= -39,507,840
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b = NumKeys * (KeySizeInBytes + 2 * NodeSize) *
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(LimbPageUtilization - LogicalPageHeaderSize + 2 * NodeSize)
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- 2 * NodeSize * (LeafPageUtilization - LogicalPageHeaderSize
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+ 2 * NodeSize)
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= 500,000 * (120 + 2 * 4) *
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(6144 - 64 + 2 * 4)
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- 2 * 4 * (6554 - 64 + 2 * 4)
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= 500,000 * 128 *
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6088
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- 8 * 6498
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= 3.896319e+11
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NumberLogicalPages = ceil[ -b/a ]
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= ceil[ -3.896319e+11/-39507840 ]
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= 9863
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TotalIndexSize = NumberLogicalPages * LogicalPageSize
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= 9863 * 8192
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= 80,797,696 bytes</pre>
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</div>
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</div>
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<div class="section"><div class="p">The equation for index size in previous versions of the operating
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system produces the following result: <pre>TotalIndexSize = (number of keys) * (key length + 8) *
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(0.8) * (1.85) + 4096
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= (NumKeys) * (KeySizeInBytes + 8) *
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(0.8) * (1.85) + 4096
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= 500000 * 128 *
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.8 * 1.85 + 4096
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= 94,724,096
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</pre>
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</div>
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</div>
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<div class="section"><p>This estimate can differ significantly from your file. The keyed
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sequence access path depends heavily on the data in your records. The only
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way to get an accurate size is to load your data and display the file description.</p>
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</div>
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<div class="section"><p>The following table shows wa list of minimum file sizes: </p>
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</div>
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<table cellpadding="4" cellspacing="0" border="1" class="tableborder"><tr><td>
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<table cellpadding="4" cellspacing="0" summary="" width="100%" border="0"><thead align="left"><tr><th align="left" valign="bottom" width="75%" id="d0e44">Description</th>
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<th align="left" valign="bottom" width="25%" id="d0e46">Minimum size</th>
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</tr>
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</thead>
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<tbody><tr><td align="left" valign="top" width="75%" headers="d0e44 ">Physical file without a member</td>
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<td align="left" valign="top" width="25%" headers="d0e46 ">8192 bytes</td>
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</tr>
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<tr><td align="left" valign="top" width="75%" headers="d0e44 ">Physical file with a single member</td>
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<td align="left" valign="top" width="25%" headers="d0e46 ">20 480 bytes</td>
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</tr>
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<tr><td align="left" valign="top" width="75%" headers="d0e44 ">Keyed sequence access path</td>
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<td align="left" valign="top" width="25%" headers="d0e46 ">12 288 bytes</td>
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</tr>
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</tbody>
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</table>
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</td></tr></table>
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<div class="section"> <div class="note"><span class="notetitle">Note:</span> Additional space is not required for an arrival sequence access
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path.</div>
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</div>
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<div class="section"><div class="p">In addition to the file sizes, the system maintains internal formats
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and directories for database files. (These internal objects are owned by user
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profile QDBSHR.) The following are estimates of the sizes of those objects: <ul><li>For any file not sharing another file's format: <img src="./delta.gif" alt="Start of change" /><p> Format size = (144 x number of fields) + 4096</p><img src="./deltaend.gif" alt="End of change" />
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</li>
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<li>For files sharing their format with any other file: <img src="./delta.gif" alt="Start of change" /><p> Format sharing directory size = (16 x number of files<br />
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sharing the format) + 4096</p><img src="./deltaend.gif" alt="End of change" />
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</li>
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<li>For each physical file and each physical file member having a logical
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file or logical file member built over it: <img src="./delta.gif" alt="Start of change" /><p> Data sharing directory size = (16 x number of files<br />
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or members sharing data) + 4096</p><img src="./deltaend.gif" alt="End of change" />
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</li>
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<li>For each file member having a logical file member sharing its access path: <img src="./delta.gif" alt="Start of change" /><p> Access path sharing directory size = (16 x number of files<br />
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or members sharing access path) + 4096</p><img src="./deltaend.gif" alt="End of change" />
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</li>
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</ul>
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</div>
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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="rbafoappmax.htm" title="When designing files on the iSeries server, you should keep in mind the sizes for database files.">Database file sizes</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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