75 lines
4.0 KiB
HTML
75 lines
4.0 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 http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="security" content="public" />
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="I/O operations on a save file" />
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<meta name="DC.Relation" scheme="URI" content="rzaiusavefiles.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2004, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2004, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="sfoperations" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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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>I/O operations on a save file</title>
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</head>
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<body id="sfoperations"><a name="sfoperations"><!-- --></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">I/O operations on a save file</h1>
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<div><p>The following considerations apply to input and output operations on a
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save file: </p>
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<ul><li>Records are always read and written sequentially. The records read from
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a save file contain sequence and parity information that is validated when
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the records are written into another save file. This information ensures that
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the records are processed in sequence and have not been changed. <p>You cannot
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write a record that has changed since it was retrieved from another save file.
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You cannot write a record that is not the next record in sequence. If you
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attempt either of these, an escape message is sent to report the error.</p>
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</li>
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<li>A read of records from the save file can be done only if the entire file
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has been written.</li>
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<li>The force-end-of-data (FEOD) function is valid for both input and output.
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<p>For an input file, FEOD signals end-of-file to the program that does the
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operation.</p>
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<p>To ensure buffered output records are not lost after an
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FEOD operation completes, they are written to the file. For an output file,
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buffered output records are not lost even if the job or system fails.</p>
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</li>
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</ul>
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<div class="section"><h4 class="sectiontitle">File-dependent attributes for a save file</h4><ul><li>The following file-dependent attributes apply when the save file is open:
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<ul><li>For input operations, the first record returned for a read operation is
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the one specified by the parameter POSITION when the file is opened. After
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the first record is read, all remaining records are returned sequentially
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to the end of the file.</li>
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<li>For output operations, new records can be added to the end of records
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already in the file (specified using the EXTEND parameter). Each save file
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record contains sequencing information used by the system to ensure that a
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record is not skipped or written more than once.</li>
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<li>If no record length is specified in the high-level language program that
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opens the file, a length of 528 bytes is assumed. If the program specifies
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a record length value, it must be 528 bytes.</li>
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</ul>
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</li>
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<li>No file-dependent parameters (such as format name) can be specified for
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read or write operations with a save file. Any file-dependent parameters specified
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are ignored.</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="rzaiusavefiles.htm">Save files</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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