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182 lines
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<meta name="DC.Title" content="Scope for a commitment definition" />
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<meta name="abstract" content="The scope of a commitment definition determines which programs will use that commitment definition, and how locks acquired during transactions are scoped." />
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<title>Scope for a commitment definition</title>
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<body id="rzakjscope"><a name="rzakjscope"><!-- --></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">Scope for a commitment definition</h1>
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<div><p>The <em>scope</em> of a commitment definition determines which programs
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will use that commitment definition, and how locks acquired during transactions
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are scoped. </p>
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<p>The interface that starts the commitment definition determines the scope
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of the commitment definition. There are four possible scopes for a commitment
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definition, which fall under two general categories:</p>
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<p><strong>Commitment definitions with job-scoped locks</strong></p>
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<ul><li>Activation-group-level commitment definition</li>
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<li>Job-level commitment definition</li>
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<li>Explicitly named commitment definition</li>
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</ul>
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<p><strong>Commitment definitions with transaction-scoped locks</strong></p>
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<ul><li>Transaction scoped commitment definition</li>
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</ul>
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<p>Commitment definitions with job-scoped locks can be used only by programs
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that run in the job that started the commitment definitions. In comparison,
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more than one job can use commitment definitions with transaction-scoped locks.</p>
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<p>Applications typically use either activation-group-level or job-level commitment
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definitions. These commitment definitions are created either explicitly with
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the Start Commitment Control (STRCMTCTL) command, or implicitly by the system
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when an SQL application runs with an isolation level other than *NONE.</p>
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<div class="section"><h4 class="sectiontitle">Activation-group-level commitment definition</h4><p>The
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most common scope is to the activation group. The activation-group-level commitment
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definition is the default scope when the STRCMTCTL command explicitly starts
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the commitment definition, or when an SQL application that runs with an isolation
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level other than No Commit implicitly starts the commitment definition. Only
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programs that run within that activation group use that commitment definition.
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Many activation-group-level commitment definitions can be active for a job
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at one time. However, each activation-group-level commitment definition can
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be associated only with a single activation group. The programs that run within
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that activation group can associate their committable changes only with that
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activation-group-level commitment definition.</p>
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<p>When iSeries™ Navigator,
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the Work with Commitment Definitions (WRKCMTDFN) command, the Display Job
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(DSPJOB) command, or the Work with Job (WRKJOB) command displays an activation-group-level
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commitment definition, these fields display the following information:</p>
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<ul><li>The commitment definition field displays the name of the activation group.
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It shows the special value *DFTACTGRP to indicate the default activation group.</li>
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<li>The activation group field displays the activation group number.</li>
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<li>The job field displays the job that started the commitment definition.</li>
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<li>The thread field displays *NONE.</li>
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</ul>
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</div>
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<div class="section"><h4 class="sectiontitle">Job-level commitment definition</h4><p>A commitment definition
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can be scoped to the job only by issuing STRCMTCTL CMTSCOPE(*JOB). Any program
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running in an activation group that does not have an activation-group-level
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commitment definition started uses the job-level commitment definition, if
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it has already been started by another program for the job. You can only start
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a single job-level commitment definition for a job.</p>
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<p>When iSeries Navigator,
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the Work with Commitment Definitions (WRKCMTDFN) command, the Display Job
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(DSPJOB) command, or the Work with Job (WRKJOB) command displays a job-level
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commitment definition, these fields display the following information:</p>
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<ul><li>The commitment definition field displays the special value *JOB.</li>
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<li>The activation group field displays a blank.</li>
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<li>The job field displays the job that started the commitment definition.</li>
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<li>The thread field displays *NONE.</li>
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</ul>
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<p>For a given activation group, the programs that run within that activation
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group can use only a single commitment definition. Therefore, programs that
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run within an activation group can either use the job-level or the activation-group-level
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commitment definition, but not both at the same time. In a multi-threaded
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job that does not use SQL server mode, transactional work for a program will
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be scoped to the appropriate commitment definition with respect to the activation
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group of the program, regardless of which thread performs it. If multiple
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threads use the same activation group, they must cooperate to perform the
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transactional work and ensure that commits and rollbacks occur at the correct
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time.</p>
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<p>Even when the job-level commitment definition is active for the
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job, a program can still start the activation-group-level commitment definition
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if no program running within that activation group has performed any commitment
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control requests or operations for the job-level commitment definition. Otherwise,
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you must first end the job-level commitment definition before you can start
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the activation-group-level commitment definition. Commitment control requests
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or operations for the job-level commitment definition that can prevent the
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activation-group-level commitment definition from being started include:</p>
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<ul><li>Opening (full or shared) a database file under commitment control.</li>
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<li>Using the Add Commitment Resource (QTNADDCR) API to add an API commitment
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resource.</li>
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<li>Committing a transaction.</li>
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<li>Rolling back a transaction.</li>
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<li>Adding a remote resource under commitment control.</li>
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<li>Using the Change Commitment Options (QTNCHGCO) API to changing commitment
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options.</li>
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<li>Bringing the commitment definition to a rollback required state using
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the Rollback Required (QTNRBRQD) API.</li>
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<li>Sending a user journal entry that includes the current commit cycle identifier
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by using the Send Journal Entry (QJOSJRNE) API with the Include Commit Cycle
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Identifier parameter.</li>
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</ul>
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<p>Likewise, if the programs within an activation group are currently
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using the activation-group-level commitment definition, the commitment definition
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must first be ended before programs running within that same activation group
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can use the job-level commitment definition.</p>
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<p>When opening a database
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file, the open scope for the opened file can be either to the activation group
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or to the job with one restriction: if a program is opening a file under commitment
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control and the file is scoped to the job, then the program making the open
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request must use the job-level commitment definition.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Explicitly-named commitment definition</h4><p>Explicitly-named
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commitment definitions are started by the system when it needs to perform
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its own commitment control transactions without affecting any transactions
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used by an application. An example of a function that starts these types of
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commitment definitions is the problem log. An application cannot start explicitly-named
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commitment definitions.</p>
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<p>When iSeries Navigator, the Work with Commitment
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Definitions (WRKCMTDFN) command, the Display Job (DSPJOB) command, or the
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Work with Job (WRKJOB) command display an explicitly-named commitment definition,
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these fields display the following information:</p>
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<ul><li>The commitment definition field displays the name given to it by the system.</li>
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<li>The activation group field displays a blank.</li>
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<li>The job field displays the job that started the commitment definition.</li>
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<li>The thread field displays *NONE.</li>
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</ul>
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</div>
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<div class="section"><h4 class="sectiontitle">Transaction-scoped commitment definitions</h4><p>Transaction-scoped
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commitment definitions are started with the XA APIs for Transaction Scoped
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Locks.</p>
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<p>These APIs use commitment control protocols that are thread based
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or SQL connection based, and not activation group based. In other words, the
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APIs are used to associate the commitment definition with a particular thread
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or SQL connection while the transactional work is performed, and to commit
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or rollback the transactions. The system attaches these commitment definitions
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to the threads that perform the transactional work, with respect to the API
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protocols. They can be used by threads in different jobs.</p>
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<p>When iSeries Navigator,
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the Work with Commitment Definitions (WRKCMTDFN) command, the Display Job
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(DSPJOB) command, or the Work with Job (WRKJOB) command display a transaction-scoped
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commitment definition, these fields display the following information:</p>
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<ul><li>The commitment definition field displays the special value *TNSOBJ.</li>
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<li>The activation group field displays a blank.</li>
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<li><img src="./delta.gif" alt="Start of change" />The job field displays the job that started the commitment
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definition. Or, if the commitment definition is currently attached to a thread,
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the thread's job is displayed.<img src="./deltaend.gif" alt="End of change" /></li>
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<li>The thread field displays the thread to which the commitment definition
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is attached (or *NONE if the commitment definition is not currently attached
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to any thread).</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 class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzakjcommitdef.htm" title="You create a commitment definition when you use the Start Commitment Control (STRCMTCTL) command to start commitment control on your system. Also, DB2 Universal Database (UDB) for iSeries automatically creates a commitment definition when the isolation level is other than No Commit.">Commitment definition</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="../apis/unix12.htm">XA APIs</a></div>
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</div>
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</div>
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