75 lines
5.1 KiB
HTML
75 lines
5.1 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 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="concept" />
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<meta name="DC.Title" content="Soft commit" />
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<meta name="abstract" content="You can improve the performance of database transactions with soft commit. Soft commit limits the number of times that the system writes journal entries associated with a transaction to disk." />
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<meta name="description" content="You can improve the performance of database transactions with soft commit. Soft commit limits the number of times that the system writes journal entries associated with a transaction to disk." />
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<meta name="DC.Relation" scheme="URI" content="rzakjoptimize.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2004, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2004, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="rzakjsoftcommi" />
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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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<!-- Use, duplication or disclosure restricted by -->
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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>Soft commit</title>
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</head>
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<body id="rzakjsoftcommi"><a name="rzakjsoftcommi"><!-- --></a>
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<img src="./delta.gif" alt="Start of change" /><!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Soft commit</h1>
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<div><p>You can improve the performance of database transactions with soft
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commit. Soft commit limits the number of times that the system writes journal
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entries associated with a transaction to disk.</p>
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<p>Soft commit can improve transaction performance, but it might cause one
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or more transactions to be lost in the event of a system failure. Traditional
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commitment control on DB2 Universal Database™ for iSeries™ ensures
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transaction durability, which means that when a transaction has been committed,
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the transaction persists on the system. Soft commit does not provide this
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durability, although it still ensures the atomicity of the transaction. In
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other words, the system guarantees a commit boundary, but one or more complete
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transactions might be lost in the event of a system failure.</p>
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<p>To use soft commit, both for a particular job or across the system, specify
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*NO on the <var class="varname">QIBM_TN_COMMIT_DURABLE</var> environment variable.
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You can change this variable with the <span class="cmdname">Add Environment Variable (ADDENVVAR)</span> command.</p>
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<p>For example, to request soft commit from a particular job, run the following
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command from the job:</p>
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<p><kbd class="userinput">ADDENVVAR ENVVAR (QIBM_TN_COMMIT_DURABLE) VALUE (*NO)</kbd></p>
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<p>To request soft commit across the system, run the following command:</p>
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<p><kbd class="userinput">ADDENVVAR ENVVAR (QIBM_TN_COMMIT_DURABLE) VALUE (*NO) LEVEL
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(*SYS)</kbd></p>
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<div class="note"><span class="notetitle">Note:</span> You must have *JOBCTL authority to set this environment variable system
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wide.</div>
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<p>If the default case <var class="varname">QIBM_TN_COMMIT_DURABLE</var> environment
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variable has not been added, or if the environment variable has been set to
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any value other than *NO, the system does not use soft commit; instead, the
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system uses traditional commitment control so that the durability of transactions
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will be ensured.</p>
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<p>You can check the existence of this new environment variable, and its value
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and level if it exists, using the <span class="cmdname">Work with Environment Variables
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(WRKENVVAR)</span> command.</p>
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<p>For some transactions, the operating system chooses to ignore your request
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for soft commit, and instead, performs traditional commitment. This happens
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in some complex environments, where multiple database connections are required
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or DDL operations are underway. The operating system can determine when it
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is appropriate to perform the request and when it makes more sense to perform
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a traditional commitment operation. So it is not harmful to request soft commit
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in such environments.</p>
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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="rzakjoptimize.htm" title="Using commitment control requires resources that can affect system performance. Several factors affect system performance regarding commitment control.">Optimize performance for commitment control</a></div>
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</div>
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</div>
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<img src="./deltaend.gif" alt="End of change" /></body>
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</html>
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