86 lines
5.3 KiB
HTML
86 lines
5.3 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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<meta name="DC.Title" content="Use separate jobs to run functions that are not threadsafe" />
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<meta name="abstract" content="There are several threadsafe mechanisms to submit a new job to complete the processing you need." />
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<meta name="description" content="There are several threadsafe mechanisms to submit a new job to complete the processing you need." />
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<title>Use separate jobs to run functions that are not threadsafe</title>
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</head>
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<body id="rzahwjob-jobco"><a name="rzahwjob-jobco"><!-- --></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">Use separate jobs to run functions that are not threadsafe</h1>
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<div><p>There are several threadsafe mechanisms to submit a new job to
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complete the processing you need. </p>
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<div class="section"><ul><li>If your application uses CL commands that are not threadsafe, you can
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use the system API <span class="apiname">Qp0zSystem()</span>. This API is similar to
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the C system() function; however, it starts a new process before running the
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CL command. It also returns some information about the results of the CL command
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that you ran. For more details about <span class="apiname">Qp0zSystem()</span>, see
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the System API Programming Reference. </li>
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<li>If your application calls APIs or programs that are not thread safe, you
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might use the <span class="apiname">spawn()</span> API to start a new job. If you use
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the <span class="apiname">spawn()</span> API, your application must decide which part
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of the application environment gets duplicated into the child. The <span class="apiname">spawn()</span> API
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allows the child process to inherit open IFS files, sockets, or other resources
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from the parent. For details about <span class="apiname">spawn()</span>, see the System
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API Programming Reference.</li>
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<li>Your application might frequently use multiple functions that are not
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thread safe. In this case, you should use one of the previously mentioned
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mechanisms to start a new job. That new job can function as a server, running
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the code that is not threadsafe when requested by your application. Your application
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can use message queues, data queues, or perhaps semaphores to communicate
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with your server. </li>
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</ul>
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</div>
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<div class="section"><div class="p">When using any of these separate job mechanisms,
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you need to be aware of the following problems involved with using a different
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job to complete some of your application processing:<ul><li>Input/output considerations:<p>The server job cannot perform normal I/O
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without conflicting with the application I/O processing. The application I/O
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processing can affect file offsets or locks that are maintained on system
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objects. Attempts at I/O can conflict between the jobs. </p>
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</li>
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<li>Parameter passing:<p>Passing pointers or other types of
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complex parameters to the functions that are not threadsafe might not be easy
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to accomplish. That function runs in a separate job. You need to solve the
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problems involved with passing complex data to that function. </p>
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</li>
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<li>Returning function calls:<p>The results from the function that is not
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threadsafe might be more complex than the simple pass/fail type of information
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that is provided by some of the mechanisms described above. This is similar
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to the parameter passing issue described above. </p>
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</li>
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<li>Job attributes:<p>You might have additional complexity to manage when
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trying to duplicate your application's environment in the server job. For
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example, if you started your application as user ALICE, and you started the
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server job as user BOB, the application behavior is not correct. </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="rzahwnonco.htm" title="Your multithreaded application at times requires access to functions or system services that are not thread safe. There are few completely safe alternatives for calling these functions.">Function calls that are not thread safe</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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