88 lines
6.0 KiB
HTML
88 lines
6.0 KiB
HTML
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<meta name="DC.Title" content="Activation groups and threads" />
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<meta name="abstract" content="All programs and service programs are activated within a substructure of a job that is called an activation group. This substructure contains the resources necessary to run the programs, including static and heap storage, and temporary data management resources." />
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<meta name="description" content="All programs and service programs are activated within a substructure of a job that is called an activation group. This substructure contains the resources necessary to run the programs, including static and heap storage, and temporary data management resources." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<title>Activation groups and threads</title>
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</head>
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<body id="rzahwgrx-grxco"><a name="rzahwgrx-grxco"><!-- --></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">Activation groups and threads</h1>
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<div><p>All programs and service programs are activated within a substructure
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of a job that is called an activation group. This substructure contains the
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resources necessary to run the programs, including static and heap storage,
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and temporary data management resources.</p>
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<div class="section"><p>In a job capable of multithreaded operation, two
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or more threads can share an activation group. A thread can run programs that
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were activated in different activation groups. The system does not keep a
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list of threads that run in an activation group or a list of activation groups
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in a thread. Ending an activation group while other threads are active in
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it can produce unpredictable results including abnormal end of the process.
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To avoid these problems, any action that ends an activation group in a secondary
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thread causes the system to end the job in an orderly fashion. In other words,
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the system ends all threads in the job, calls exit routines and C++ destructors
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in the initial thread, and finally closes the files.</p>
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</div>
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<div class="section"><div class="p">When working with activation groups, consider
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the following items:<ul><li>Return from activation groups:<p>Programs created with <span class="parmname">ACTGRP(*NEW)</span> get
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a new activation group every time it is called. When the program returns,
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the new activation group ends. In jobs capable of multithreaded operation,
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returning from programs that were created with <span class="parmname">ACTGRP(*NEW)</span> will
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end the job.</p>
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<p>Both <span class="filepath">default</span> and <span class="filepath">named</span> activation
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groups are persistent. The <span class="filepath">Default</span> activation group is
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created when a job starts and is destroyed only when the job ends. <span class="filepath">Named</span> activation
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groups are created when they are first needed in a job. A normal return from
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the named activation group leaves the activation group in last-used state,
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but does not delete the activation group. Hence, in a job capable of multithreaded
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operations, a normal return from the <span class="filepath">default</span> or <span class="filepath">named</span> activation
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group does not cause the job to end. </p>
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<p>Using <span class="apiname">exit()</span> or <span class="apiname">abort()</span> in
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any activation group in a secondary thread always ends the job.</p>
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</li>
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<li>Unhandled exceptions:<p>If an exception has not been handled by the time
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it has percolated to the control boundary and the control boundary is a program
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entry procedure (PEP or main entry point), the multithread-capable job is
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ended. </p>
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</li>
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<li><span class="cmdname">Reclaim activation group (RCLACTGRP)</span>:<p>Jobs
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capable of multithreaded operation allow this command to be called only in
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the initial thread on the job. If secondary user threads are present in the
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job, this command sends a CPF180B escape message to the caller of the command.</p>
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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="rzahwas4co.htm" title="All programs have at least one thread, referred to as the initial thread. In a program with multiple threads, each thread runs its code independently of the other threads in the program.">Threads on i5/OS</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="rzahwsafco.htm" title="A function is threadsafe if you can start it simultaneously in multiple threads within the same process. A function is threadsafe if and only if all the functions it calls are also threadsafe.">Thread safety</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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