91 lines
4.9 KiB
HTML
91 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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<meta name="DC.Type" content="task" />
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<meta name="DC.Title" content="Override file attributes" />
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<meta name="abstract" content="Find out why file attributes are built. You can also see a override file attribute example." />
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<meta name="description" content="Find out why file attributes are built. You can also see a override file attribute example." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2004, 2006" />
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<meta name="DC.Identifier" content="ovfatt" />
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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>Override file attributes</title>
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</head>
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<body id="ovfatt"><a name="ovfatt"><!-- --></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">Override file attributes</h1>
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<div><p>Find out why file attributes are built. You can also see a override
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file attribute example.</p>
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<div class="section"> <p>File attributes are built as
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a result of the following:</p>
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<ul><li>Create file command. Initially, this command builds the file attributes.</li>
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<li>Program
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using the files. At compile time, the user program can specify some of the
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file attributes. The high-level language used by the program determines the
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attributes that can be used.</li>
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<li>Override commands. At program run time, these commands can override the file
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attributes previously built by the merging of the file description and the
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file parameters specified in the user program.</li>
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</ul>
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<p>The simplest form of overriding a file is to override some attribute
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of the file.</p>
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<p>For example, assume that you create a tape file OUTPUT
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whose attributes are:</p>
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<ul><li>Use Device TAP01.</li>
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<li>Write the Data on the tape with a density of 1600 bits per inch (bpi)</li>
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<li>Use the ASCII character code type.</li>
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<li>When you close the tape file, the program rewinds and unloads the tape.</li>
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</ul>
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<div class="p"> The Create Tape File (CRTTAPF) command looks like this: <pre>CRTTAPF FILE(QGPL/OUTPUT) DEV(TAP01)
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DENSITY(1600) CODE(*ASCII) ENDOPT(*UNLOAD)</pre>
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</div>
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<div class="p">Your
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application program has the tape file OUTPUT specified with a character code
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type of EBCDIC and a density of 3200. However, before you run the application
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program, you want to change the density to 6250 bpi and the end option to
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*REWIND. The override command looks like this: <pre>OVRTAPF FILE(OUTPUT) DENSITY(6250)
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ENDOPT(*REWIND)</pre>
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</div>
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<p>When you call the application program,
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the system uses a tape density of 6250 bpi and the end option is *REWIND.</p>
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<p>When
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the application program opens the file, the system merges these
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to form the open data path (ODP):</p>
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<ul><li>The file overrides.</li>
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<li>The program-specified attributes.</li>
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<li>The file attributes.</li>
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</ul>
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<p>The program uses the open data path (ODP) during
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the running of the program. File overrides have precedence overprogram-specified
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attributes. Program-specified attributes have precedence over file-specified
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attributes. In <a href="#ovfatt__rbahh524.eps">Figure 1</a>, when you open the
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file and you perform output operations, the program writes:</p>
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<ul><li>To the device TAP01 with a density of 6250 bpi.</li>
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<li>In a character code type of EBCDIC.</li>
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<li>An end option of *REWIND.</li>
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</ul>
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<p><a href="#ovfatt__rbahh524.eps">Figure 1</a> explains this example.</p>
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<div class="fignone" id="ovfatt__rbahh524.eps"><a name="ovfatt__rbahh524.eps"><!-- --></a><span class="figcap">Figure 1. Override file attributes</span><br /><img src="rbahh524.gif" alt="This diagram is explained
in the example mentioned above." /><br /></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="overide.htm" title="Learn what can be done with an override and how to manage the overrides that currently exist.">Use overrides</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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