115 lines
7.2 KiB
HTML
115 lines
7.2 KiB
HTML
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<meta name="DC.Title" content="DDS logical files with more than one record format" />
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<meta name="abstract" content="When you specify more than one record format in a logical file, you must specify at least one key field for every record format in the logical file." />
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<title>DDS logical files with more than one record format</title>
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</head>
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<body id="logmultrecfmts"><a name="logmultrecfmts"><!-- --></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">DDS logical files with more than one record format</h1>
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<div><p>When you specify more than one record format in a logical file,
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you must specify at least one key field for every record format in the logical
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file.</p>
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<p>It is not necessary to specify the same number of key fields in each key.
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Also, key fields specified in one record format must have the same field attributes
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and access path keywords as the corresponding key fields in other record formats
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in the same logical file. Variable-length key fields are not be allowed to
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align with a fixed-length key field, even if the field types and lengths are
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the same.</p>
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<p>A key is required for every record format so that the logical file members
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can have a single access path sequencing records of each record format. When
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records are returned from the various members of the physical file on which
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the logical file is based, they are merged according to the values of the
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key fields in the access path for the logical file member.</p>
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<p>When records of a logical file member are sequenced, the operating system
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builds a <em>key value</em> for each record by concatenating the values in its
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key fields. The key value is then used to build the access path for use by
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your program. </p>
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<p>Each key field in a composite key has a <em>key position</em>. The first
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key field specified is in position 1, the second key field specified is in
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position 2, and so on. During I/O operations to a logical file, the <span class="keyword">i5/OS™</span> program compares the key values
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of the records written to or read from the database. When you create a logical
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file that has more than one record format (with or without different key fields
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specified), the operating system performs <em>key position attribute checking</em>.
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For key position attribute checking to succeed, key fields of different record
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formats that are in the same key positions must have the same data type, length,
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decimal positions, and access path keywords specified at the key field level.
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This ensures a meaningful record sequence from the comparisons made during
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an I/O operation.</p>
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<p>Floating-point fields used as key fields must have the same data type and
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precision but need not have the same length and decimal positions.</p>
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<p>In the following example, FIELD1, FLD1, and F1 must have the same attributes,
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and FIELD2, FLD2, and F2 must have the same attributes. FIELD1, FLD1, and
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F1 are in key position 1; FIELD2, FLD2, and F2 are in key position 2. One
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record format can have more key fields than another, and the additional fields
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do not need key position attribute checking. FLD3 is such a field.</p>
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<div class="fignone" id="logmultrecfmts__cfig5"><a name="logmultrecfmts__cfig5"><!-- --></a><span class="figcap">Figure 1. Key field attribute checking</span><pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
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00010A R RECORD1 PFILE(PF1)
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00020A FIELD1 5 0
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00030A FIELD2 10
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00040A FIELD3 10
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00050A K FIELD1
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00060A K FIELD2 DESCEND
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00070A*
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00080A R RECORD2 PFILE(PF2)
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00090A FLD1 5 0
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00100A FLD2 10
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00110A FLD3 20
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00120A K FLD1
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00130A K FLD2 DESCEND
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00140A K FLD3
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A*
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A R RECORD3 PFILE(PF3)
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A F1 5 0
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A F2 10
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A F3 30
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A K F1
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A K F2 DESCEND
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A
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A</pre>
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</div>
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<p>In examples of key fields in a logical file with more
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than one record format, fields named ITEM are specified in each key. For record
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formats INVFMT and ACTFMT, ITEM is the only key field specified. For record
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format ORDFMT, a composite key is specified. This composite key includes ITEM,
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SHPYR, SHPMO, and SHPDA. Each of the fields used in a key must also exist
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at the field level. Therefore, ITEM must exist in the record format for the
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physical file INVENTORY so that it can be copied into this logical file for
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INVFMT. Also, ITEM must exist in the record format for the logical file ACCOUNTL
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so that it can be copied into this logical file for ACTFMT. ITEM must also
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exist in physical file ACCOUNTS.</p>
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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="lkeynm.htm" title="When you specify K in position 17, the name specified in positions 19 through 28 is a key field name.">Key field name</a></div>
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</div>
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<div class="reltasks"><strong>Related tasks</strong><br />
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<div><a href="simpmult.htm" title="You must specify the PFILE keyword at the record level for simple and multiple format logical files. In a multiple format logical file, a record format can use only the fields common to all the physical files specified on the PFILE keyword for that record format.">Simple and multiple format logical files in 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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