115 lines
8.3 KiB
HTML
115 lines
8.3 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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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Commitment definition for two-phase commit: Indicate OK to leave out" />
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<meta name="abstract" content="Normally, the transaction manager at every location in the transaction program network participates in every commit or rollback operation. To improve performance, you can set up some or all locations in a transaction to allow the transaction manager to indicate OK to leave out." />
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<meta name="description" content="Normally, the transaction manager at every location in the transaction program network participates in every commit or rollback operation. To improve performance, you can set up some or all locations in a transaction to allow the transaction manager to indicate OK to leave out." />
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<meta name="DC.Relation" scheme="URI" content="rzakjcommitdefs_tp.htm" />
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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.Identifier" content="rzakjokleaveout" />
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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>Commitment definition for two-phase commit: Indicate OK to leave out</title>
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</head>
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<body id="rzakjokleaveout"><a name="rzakjokleaveout"><!-- --></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">Commitment definition for two-phase commit: Indicate OK to leave out</h1>
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<div><p>Normally, the transaction manager at every location in the transaction
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program network participates in every commit or rollback operation. To improve
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performance, you can set up some or all locations in a transaction to allow
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the transaction manager to indicate OK to leave out.</p>
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<div class="note"><span class="notetitle">Note:</span> The Indicate OK to leave out option does not apply if you are using
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a DRDA<sup>®</sup> distributed
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unit of work over TCP/IP connection.</div>
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<p>If no communications flows are sent to the location during a transaction,
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the location is left out when a commit or rollback operation is performed.
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This improves overall performance because the communications flows that normally
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occur during the commit or rollback are eliminated during transactions in
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which no data is sent to one or more remote locations.</p>
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<p>After you start commitment control, you can use the Change Commitment Options
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(QTNCHGCO) API to change the OK to leave out option to Y (Yes). You might
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want to do this if one or more remote systems often are not involved in a
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transaction.</p>
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<p>If your commitment definition is set up to indicate OK to leave out, the
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application waits for the next message flow from another location.</p>
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<p>The OK to leave out option is intended for applications that are client/server
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in nature. If the only purpose of program A is to satisfy requests from program
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I and not to do any independent work, then it is appropriate to allow the
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OK to leave out option for program A.</p>
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<div class="section" xml:lang="en-us" id="rzakjokleaveout__flowcommitprocagenptimizwhenagentvotes"><a name="rzakjokleaveout__flowcommitprocagenptimizwhenagentvotes"><!-- --></a><h4 class="sectiontitle">Flow
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of commit processing without last agent optimization when agent votes OK to
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leave out</h4><p>The following figure shows the flow of messages among
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the application programs and the transaction managers when an application
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program issues a commit instruction without last agent optimization when the
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agent indicates OK to leave out. Both the initiator application program and
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the agent application programs are unaware of the two-phase commit processing.
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The numbers in parentheses () in the figure correspond to the numbered items
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in the description that follows.</p>
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<br /><img src="rzakj514.gif" alt="Flow of commit processing without last agent optimization when agent votes OK to leave out" /><br /><p>Here is a description of
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the events for normal processing without last agent optimization when the
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agent votes OK to leave out. This describes a basic flow. The sequence of
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events can become much more complex when the transaction program network has
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multiple levels or when errors occur.</p>
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<ol><li>Application program A does a receive request to indicate that it is ready
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to receive a request from program I.</li>
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<li>The initiator application (I) issues a commit instruction.</li>
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<li>The transaction manager for the initiator (TM-I) takes the role of initiator
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for this transaction. It starts the prepare wave by sending a prepare message
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to all the other locations that are participating in the transaction.</li>
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<li>The transaction managers for every other location take the role of agent
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(TM-A). The application program A is notified by TM-A that a request to commit
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has been received. For ICF files, the notification is in the form of the Receive
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Take Commit (RCVTKCMT) ICF indicator being set on.</li>
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<li>The application program A responds by issuing a commit instruction (or
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a rollback instruction). This is the application program's vote.</li>
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<li>If application program A has used the Change Commitment Options API (QTNCHGCO)
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to set the OK to leave out commitment option to Y, an indicator is sent when
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the agent (TM-A) responds to the initiator (TM-I) with a request commit message.<div class="note"><span class="notetitle">Note:</span> Any
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change to the OK to leave out commitment option does not take effect until
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the next successful commit operation.</div>
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</li>
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<li>When the initiator (TM-I) receives all the votes, the TM-I sends a commit
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message. This starts the committed wave.</li>
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<li>Each agent (TM-A) commits and responds with a reset message.</li>
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<li>A return is sent to the application program (I) to indicate that the transaction
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is complete at the initiator.</li>
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<li>Any number of transactions might occur on TM-I, none of which requires
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changes to TM-A or data from TM-A. TM-A is not included in these transactions.</li>
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<li>The next time the initiator (TM-I) issues a message to the agent (A),
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a new transaction ID is sent with the message. If the initiator performs any
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commit or rollback operations before sending a message to the agent, no messages
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are sent to the agent during those operations (the agent is 'left out' of
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those commits or rollbacks). Because one or more transactions might have been
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committed or rolled back at the initiator while the agent was left out, the
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initiator must communicate its current transaction ID when the next message
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is sent to the agent.</li>
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<li>A return is sent to the application program (A) to indicate that the original
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commit is complete and that it is participating in the current transaction.</li>
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</ol>
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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="rzakjcommitdefs_tp.htm" title="After you start commitment control, you can use the Change Commitment Options (QTNCHGCO) API to change the commitment options for your transaction.">Commitment definitions for two-phase commitment control</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><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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</body>
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</html>
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