126 lines
7.6 KiB
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126 lines
7.6 KiB
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<meta name="DC.Title" content="Define logical file members" />
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<meta name="abstract" content="You can define members in logical files to separate the data into logical groups. The logical file member can be associated with one or several physical file members." />
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<title>Define logical file members</title>
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<body id="rbafologfm"><a name="rbafologfm"><!-- --></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">Define logical file members</h1>
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<div><p>You can define members in logical files to separate the data into
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logical groups. The logical file member can be associated with one or several
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physical file members.</p>
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<p>The following chart illustrates this concept:</p>
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<br /><img src="rbafo506.gif" alt="Logical file members" /><br /><p>The record formats used with all logical members in a logical file must
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be defined in data description specifications (DDS) when the file is created.
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If new record formats are needed, another logical file or record format must
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be created.</p>
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<p>The attributes
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of an access path are determined by the information specified in DDS and on
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commands when the logical file is created. The selection of data members is
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specified in the DTAMBRS parameter on the Create Logical File (CRTLF) and
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Add Logical File Member (ADDLFM) commands.</p>
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<p>When a logical file is defined, the physical files used by the logical
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file are specified in DDS by the record-level PFILE or JFILE
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keyword. If multiple record formats are defined in DDS, a PFILE keyword must
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be specified for each record format. You can specify one or more physical
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files for each PFILE keyword.</p>
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<p>When a logical file is created
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or a member is added to the file, you can use the DTAMBRS parameter on the
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CRTLF or the ADDLFM command to specify which members of the physical files
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used by the logical file are to be used for data. *NONE can be specified as
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the physical file member name if no members from a physical file are to be
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used for data.</p>
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<p>In the following example, the logical file has two record formats defined:</p>
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<pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
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A
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00010A R LOGRCD2 PFILE(PF1 PF2)
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A .
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A .
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A .
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00020A R LOGRCD3 PFILE(PF1 PF2 PF3)
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A .
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A .
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A .
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A</pre>
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<div class="p">If the DTAMBRS parameter is specified on the CRTLF or ADDLFM command as
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in the following example: <pre>DTAMBRS((PF1 M1) (PF2 (M1 M2)) (PF1 M1) (PF2 (*NONE)) (PF3 M3))</pre>
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</div>
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<p>Record format LOGRCD2 is associated with physical file member M1 in PF1
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and M1 and M2 in file PF2. Record format LOGRCD3 is associated with M1 in
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PF1 and M3 in PF3. No members in PF2 are associated with LOGRCD3. If the same
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physical file name is specified on more than one PFILE keyword, each occurrence
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of the physical file name is handled as a different physical file.</p>
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<p>If a library name is not specified for the file on the PFILE keyword, the
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library list is used to find the physical file when the logical file is created.
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The physical file name and the library name then become part of the logical
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file description. The physical file names and the library names specified
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on the DTAMBRS parameter must be the same as those stored in the logical file
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description.</p>
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<p>If a file name is not qualified by a library name on the DTAMBRS parameter,
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the library name defaults to *CURRENT, and the system uses the library name
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that is stored in the logical file description for the respective physical
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file name. This library name is either the library name that was specified
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for the file on the PFILE DDS keyword or the name of the library in which
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the file was found using the library list when the logical file was created.</p>
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<div class="p">When you add a member to a logical file, you can specify data members as
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follows: <ul><li>Specify no associated physical file members (DTAMBRS (*ALL) default).
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The logical file member is associated with all the physical file members of
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all physical files in all the PFILE keywords specified in the logical file
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DDS.</li>
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<li>Specify the associated physical file members (DTAMBRS parameter). If you
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do not specify library names, the logical file determines the libraries used.
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When more than one physical file member is specified for a physical file,
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the member names should be specified in the order in which records are to
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be retrieved when duplicate key values occur across those members. If you
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do not want to include any members from a particular physical file, either
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do not specify the physical file name or specify the physical file name and
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*NONE for the member name. This method can be used to define a logical file
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member that contains a subset of the record formats defined for the logical
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file.</li>
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</ul>
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</div>
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<div class="p">You can use the Create Logical File (CRTLF) command to create the first
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member when you create the logical file. Subsequent members must be added
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using the Add Logical File Member (ADDLFM) command. However, if you are going
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to add more members, you must specify more than 1 for the MAXMBRS parameter
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on the CRTLF command. The following example of adding a member to a logical
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file uses the CRTLF command. <pre>CRTLF FILE(DSTPRODLB/ORDHDRL)
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MBR(*FILE) DTAMBRS(*ALL)
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TEXT('Order header logical file')</pre>
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</div>
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<p>*FILE is the default for the MBR parameter and means that the name of the
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member is the same as the name of the file. All the members of the associated
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physical file (ORDHDRP) are used in the logical file (ORDHDRL) member. The
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text description is the text description of the member.</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="rbafocrlof.htm" title="This topic shows how to create a logical file using data description specifications (DDS).">Create a logical file</a></div>
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</div>
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