83 lines
4.9 KiB
HTML
83 lines
4.9 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 name="DC.Type" content="task" />
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<meta name="DC.Title" content="Managing media capacity on a per-file basis" />
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<meta name="abstract" content="Learn how to manage media capacity on a per-file basis." />
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<meta name="description" content="Learn how to manage media capacity on a per-file basis." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2000, 2006" />
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<meta name="DC.Identifier" content="capacitymanage" />
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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>Managing media capacity on a per-file basis</title>
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</head>
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<body id="capacitymanage"><a name="capacitymanage"><!-- --></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">Managing media capacity on a per-file basis</h1>
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<div><p>Learn how to manage media capacity on a per-file basis.</p>
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<div class="p"><div class="p">An application might need to manage the media capacity on a per-file
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basis. Following are a few methods you can use to decide if a file will fit
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on the media: <ol><li>Handle error on a close operation <p>Assume an optical volume is initialized
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to a 95% threshold and an application writes files until the volume threshold
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is reached. When the threshold is reached, the application will receive message
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CPF1F61, <kbd class="userinput">No free space available on media</kbd>. At this
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point, the volume threshold can be increased to 97% (or anything else up to
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100%) by using the CHGOPTVOL command. You can then attempt to close the file.</p>
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</li>
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<li>Specify QALCSIZE on the Open Stream File HFS API <div class="p">Another method to
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determine if a file will fit on a volume is by specifying an allocation size
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(QALCSIZE) on an open stream file. On an open stream file, the system can
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pass a value in attribute QALCSIZE. This attribute is valid when the open
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operation is for create or replace; otherwise, it is ignored. Specifying a
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value for QALCSIZE results in comparing the specified value against the space
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available on the volume. If the space available is less than QALCSIZE, then
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the system issues message CPF1F61. The space available must exceed the QALCSIZE
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in order for the open operation to occur. Only on the first open instance
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of a file honors this attribute. If specified by more than one opening of
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a file, the system ignores the additional attributes. <div class="note"><span class="notetitle">Note:</span> This does not
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actually allocate space on the optical volume at the time of the open operation.
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It checks the volume to see if the number of requested bytes
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are available.</div>
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</div>
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<div class="p">There are drawbacks to using this method: <ol type="a"><li>You need to know the size of the file you are creating at the time you
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make the open request.</li>
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<li>If multiple jobs are writing to the same media, there is no guarantee
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that by the time the data is written, the space will still be available.</li>
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</ol>
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</div>
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<p>If the size of the file is known prior to the time the open request
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is made, and there will not be other jobs writing to that volume during the
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time your file is open, this is an excellent method to check media capacity
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before creating a file.</p>
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</li>
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<li>Retrieve space available on a volume <p>Another method is to have the
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application retrieve the space available on the volume. You can do this by
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using the Display Optical (DSPOPT) command through output file support. The
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output file can then be read to retrieve the number of bytes assumed to be
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available on the media.</p>
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</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>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="tipsandtechniques.htm" title="The following techniques are often helpful in designing custom optical programs for your business.">Tips: Optical programming</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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