119 lines
7.4 KiB
HTML
119 lines
7.4 KiB
HTML
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<meta name="DC.Title" content="Override considerations to System/36 for DDM" />
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<meta name="abstract" content="When a file override is issued on the iSeries server to get records in a logical file on a System/36, the results might be different than expected because of the difference in how each system deals with keyed files." />
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<meta name="description" content="When a file override is issued on the iSeries server to get records in a logical file on a System/36, the results might be different than expected because of the difference in how each system deals with keyed files." />
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<meta name="DC.subject" content="target DDM (TDDM), System/36, override considerations, TDDM (target DDM), recursion level, override considerations, logical file" />
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<meta name="keywords" content="target DDM (TDDM), System/36, override considerations, TDDM (target DDM), recursion level, override considerations, logical file" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1999, 2006" />
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<title>Override considerations to System/36 for
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DDM</title>
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</head>
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<body id="rbae5ovr3836"><a name="rbae5ovr3836"><!-- --></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 considerations to <span class="keyword">System/36</span> for
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DDM</h1>
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<div><p>When a file override is issued on the <span class="keyword">iSeries™ server</span> to
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get records in a logical file on a <span class="keyword">System/36™</span>,
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the results might be different than expected because of the difference in
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how each system deals with keyed files.</p>
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<div class="section"><p>An <span class="keyword">iSeries server</span> uses
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access paths and logical files, which produce a single view of a file. A <span class="keyword">System/36</span> logical file can be considered
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a list of keys and relative record numbers.</p>
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</div>
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<div class="section"><p>When an <span class="keyword">iSeries server</span> accesses
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a <span class="keyword">System/36</span> logical file:</p>
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<ul><li>If you specify a relative record number, you receive the record from the
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underlying <span class="keyword">System/36</span> base file
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that corresponds to that record number. Then if you request to read the next
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record, you receive the next sequential record from the base file.</li>
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<li>If you specify a key, you receive the record that corresponds to the first
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occurrence of that key in the index file. If you request to read the next
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record, you receive the record that matches the next entry in the index file.</li>
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</ul>
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</div>
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<div class="section"><p>The following example shows the various results for records being
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retrieved from a <span class="keyword">System/36</span> logical
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file by an <span class="keyword">iSeries</span> program.
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The example assumes that:</p>
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<ul><li>File S36FILEA is the base file and S36FILEB is the logical file that is
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built over the base file.</li>
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<li>Both files have DDM files named S36FILEA and S36FILEB that point to corresponding
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remote files on the target <span class="keyword">System/36</span>.</li>
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<li>The key field is numeric and it always contains the record number.</li>
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<li>The records in the base file (S36FILEA) are in ascending sequence by key,
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and the records in the logical file (S36FILEB) are in descending sequence
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with the same key.</li>
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<li>To create the results shown in the following table, the POSITION parameter
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value is shown to vary, and no NBRRCDS parameter is specified on either command
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(which means the total records read is dependent only on the POSITION parameter
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value).<pre>OVRDBF FILE(S36FILEA) TOFILE(S36FILEB)
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POSITION(*RRN ... or *KEY ...)
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CPYF FROMFILE(S36FILEA) TOFILE(ISERIESFILEB)
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CRTFILE(*YES) FMTOPT(*NOCHK)</pre>
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</li>
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</ul>
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</div>
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<div class="section"><p>Depending on the values specified on the <span class="cmdname">Override with
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Database File (OVRDBF)</span> command for the POSITION parameter, the following
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are the resulting records that are copied into the file ISERIESFILEB when
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it is created on the source <span class="keyword">iSeries server</span>:</p>
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</div>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" width="100%" frame="border" border="1" rules="all"><thead align="left"><tr><th align="left" valign="bottom" width="50%" id="d0e142">POSITION parameter (See note)</th>
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<th align="left" valign="bottom" width="50%" id="d0e144">Resulting records retrieved</th>
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</tr>
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</thead>
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<tbody><tr><td align="left" valign="top" width="50%" headers="d0e142 ">*RRN 1</td>
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<td align="left" valign="top" width="50%" headers="d0e144 ">299 records, 1 through 299</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e142 ">*KEY 1</td>
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<td align="left" valign="top" width="50%" headers="d0e144 ">1 record, first record only</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e142 ">*RRN 299</td>
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<td align="left" valign="top" width="50%" headers="d0e144 ">1 record, last record only</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e142 ">*KEY 299</td>
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<td align="left" valign="top" width="50%" headers="d0e144 ">299 records, 299 through 1</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e142 ">*RRN 150</td>
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<td align="left" valign="top" width="50%" headers="d0e144 ">150 records, 150 through 299</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e142 ">*KEY 150</td>
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<td align="left" valign="top" width="50%" headers="d0e144 ">150 records, 150 through 1</td>
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</tr>
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<tr><td colspan="2" align="left" valign="top" headers="d0e142 d0e144 "><div class="note"><span class="notetitle">Note:</span> This
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column assumes only one key field for *KEY values and uses the remote file
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name as the default value for the record format name.</div>
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</td>
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</tr>
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</tbody>
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</table>
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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="rbae5source36.htm" title="Before an iSeries server can access files on a System/36, Level 1.0 of the DDM architecture must be installed on the System/36. These topics contain information that applies when an iSeries server is the source or target server communicating with a System/36.">System/36 source and target considerations for DDM</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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