53 lines
3.6 KiB
HTML
53 lines
3.6 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 name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Checksum protection in a distributed relational database" />
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<meta name="abstract" content="Checksum protection guards against data loss on any disk in an auxiliary storage pool (ASP)." />
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<meta name="description" content="Checksum protection guards against data loss on any disk in an auxiliary storage pool (ASP)." />
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<meta name="DC.subject" content="database recovery, checksum protection, recovery, disk failure, checksum protection" />
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<meta name="keywords" content="database recovery, checksum protection, recovery, disk failure, checksum protection" />
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<meta name="DC.Relation" scheme="URI" content="rbal1datarecov.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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<!-- All rights reserved. Licensed Materials Property of IBM -->
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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>Checksum protection in a distributed relational database</title>
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</head>
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<body id="rbal1checksum"><a name="rbal1checksum"><!-- --></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">Checksum protection in a distributed relational database</h1>
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<div><p>Checksum protection guards against data loss on any
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disk in an auxiliary storage pool (ASP).</p>
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<div class="section"><p>The checksum software maintains a coded copy of ASP data in special
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checksum data areas within that ASP. Any changes made to permanent objects
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in a checksum protected ASP are automatically maintained in the checksum data
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of the checksum set. If any single disk unit in a checksum set is lost, the
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server reconstructs the contents of the lost device using the checksum and
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the data on the remaining functional units of the set. In this way, if any
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one of the units fails, its contents can be recovered. This reconstructed
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data reflects the most up-to-date information that was on the disk at the
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time of the failure. Checksum protection can affect server performance significantly.
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In a distributed relational database, this might be a concern.</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="rbal1datarecov.htm" title="Recovery is not possible for recently entered data if a disk failure occurs and all objects are not saved on tape or disk immediately before the failure. After previously saved objects are restored, the server is operational, but the database is not current.">Data recovery after disk failures for distributed relational databases</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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