109 lines
7.3 KiB
HTML
109 lines
7.3 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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<head>
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Share existing record format descriptions in a database file" />
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<meta name="abstract" content="A record format can be described once in either a physical or a logical file (except a join logical file) and can be used by many files. When you describe a new file, you can specify that the record format of an existing file is to be used by the new file." />
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<meta name="description" content="A record format can be described once in either a physical or a logical file (except a join logical file) and can be used by many files. When you describe a new file, you can specify that the record format of an existing file is to be used by the new file." />
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<meta name="DC.subject" content="sharing, record format descriptions that exist, record format, description, sharing existing, sharing existing record format" />
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<meta name="keywords" content="sharing, record format descriptions that exist, record format, description, sharing existing, sharing existing record format" />
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<meta name="DC.Relation" scheme="URI" content="rbafodescdds.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbaforcdfmtr.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Share existing record format descriptions in a database file</title>
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</head>
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<body id="rbafosharf"><a name="rbafosharf"><!-- --></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">Share existing record format descriptions in a database file</h1>
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<div><p>A record format can be described once in either a physical or a
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logical file (except a join logical file) and can be used by many files. When
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you describe a new file, you can specify that the record format of an existing
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file is to be used by the new file.</p>
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<p>Sharing existing record format descriptions can help reduce the number
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of DDS statements that you normally code to describe a record format in a
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new file and can save auxiliary storage space.</p>
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<p>The file originally describing the record format can be deleted without
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affecting the files sharing the record format. After the last file using the
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record format is deleted, the system automatically deletes the record format
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description.</p>
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<p>The following example shows the DDS for two files. The first file describes
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a record format, and the second file shares the record format of the first
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file:</p>
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<pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
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A R RECORD1 PFILE(CUSMSTP)
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A CUST
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A NAME
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A ADDR
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A SEARCH
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A K CUST
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A</pre>
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<pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
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A R RECORD1 PFILE(CUSMSTP)
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A FORMAT(CUSMSTL)
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A K NAME
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A</pre>
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<p>The first example shows file CUSMSTL, in which the fields <em>Cust</em>, <em>Name</em>, <em>Addr</em>,
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and <em>Search</em> make up the record format. The <em>Cust</em> field is specified
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as a key field.</p>
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<p>The DDS in the second example shows file CUSTMSTL1,
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in which the FORMAT keyword names CUSMSTL to supply the record format. The
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record format name must be RECORD1, the same as the record format name shown
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in the first example. Because the files are sharing the same format, both
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files have fields <em>Cust</em>, <em>Name</em>, <em>Addr</em>, and <em>Search</em> in
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the record format. In file CUSMSTL1, a different key field, <em>Name</em> is
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specified.</p>
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<div class="p">The following restrictions apply to shared record formats: <ul><li>A physical file cannot share the format of a logical file.</li>
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<li>A join logical file cannot share the format of another file, and another
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file cannot share the format of a join logical file.</li>
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<li>A view cannot share the format of another file, and another file cannot
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share the format of a view. (In the Structured Query Language (SQL), a <em>view</em> is
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an alternative representation of data from one or more tables. It can include
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all or some of the columns contained in the table or tables on which it is
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defined.)</li>
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</ul>
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</div>
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<p>If the original record format is changed by deleting all related files
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and creating the original file and all the related files again, it is changed
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for all files that share it. If only the file with the original format is
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deleted and re-created with a new record format, all files previously sharing
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that file's format continue to use the original format.</p>
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<p>If a logical file is defined but no field descriptions are specified and
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the FORMAT keyword is not specified, the record format of the first physical
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file (specified first on the PFILE keyword for the logical file) is automatically
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shared. The record format name specified in the logical file must be the same
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as the record format name specified in the physical file.</p>
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<p>To find out if a file shares a format with
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another file, use the RCDFMT parameter on the Display Database Relations (DSPDBR)
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command. </p>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rbaforcdfmtr.htm">Record format relationships between physical and logical database files</a></strong><br />
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When you change, add, and delete fields with the Change Physical File (CHGPF) command, a certain relationship exists between the physical and logical files that share the same record format.</li>
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<li class="ulchildlink"><strong><a href="rbaforcdfmts.htm">Record format sharing limitation with physical and logical database files</a></strong><br />
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You might encounter this record format sharing limitation when you are duplicating the same database object multiple times.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rbafodescdds.htm" title="When you describe a database file using data description specifications (DDS), you can describe information at the file, record-format, join, field, key, and select/omit levels.">Describe database files using DDS</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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