91 lines
5.2 KiB
HTML
91 lines
5.2 KiB
HTML
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<meta name="DC.Title" content="CPI4326 - &12 &13 processed in join position &10" />
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<title>CPI4326 - &12 &13 processed in join position &10</title>
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</head>
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<body id="cpi4326"><a name="cpi4326"><!-- --></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">CPI4326 - &12 &13 processed in join position &10</h1>
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<div>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><thead align="left"><tr><th colspan="2" align="center" valign="middle" id="d0e16">CPI4326</th>
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</tr>
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</thead>
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<tbody><tr valign="middle"><td valign="middle" width="26.02040816326531%" headers="d0e16 ">Message Text:</td>
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<td valign="middle" width="73.9795918367347%" headers="d0e16 ">&12 &13 processed in join position &10.</td>
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</tr>
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<tr valign="middle"><td valign="middle" width="26.02040816326531%" headers="d0e16 ">Cause Text:</td>
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<td valign="middle" width="73.9795918367347%" headers="d0e16 ">Access path for member &5 of file &3 in library &4 was
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used to access records in member &2 of file &13 in library &1
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for reason code &9. The reason codes and their meanings follow: <ol><li>Perform specified record selection.</li>
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<li>Perform specified ordering/grouping criteria.</li>
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<li>Record selection and ordering/grouping criteria.</li>
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<li>Perform specified join criteria.</li>
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</ol>
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If file &13 in library &1 is a logical file then member &8
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of physical file &6 in library &7 is the actual file in join position &10.
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<p></p>
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A file name starting with *TEMPX for the access path indicates
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it is a temporary access path built over file &6. <p></p>
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A file name
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starting with *N or *QUERY for the file indicates it is a temporary file.
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<p></p>
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Index only access was used for this file within the query: &11.
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<p></p>
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A value of *YES for index only access processing indicates
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that all of the fields used from this file for this query can be found within
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the access path of file &3. A value of *NO indicates that index only access
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could not be performed for this access path.<p></p>
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Index only
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access is generally a performance advantage since all of the data can be extracted
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from the access path and the data space does not have to be paged into active
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memory.</td>
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</tr>
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<tr valign="middle"><td valign="middle" width="26.02040816326531%" headers="d0e16 ">Recovery Text:</td>
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<td valign="middle" width="73.9795918367347%" headers="d0e16 ">Generally, to force a file to be processed in join position 1, specify
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an order by field from that file only. <p></p>
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If ordering is desired,
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specifying ORDER BY fields over more than one file forces the creation of
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a temporary file and allows the optimizer to optimize the join order of all
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the files. No file is forced to be first. <p></p>
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An access path can
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only be considered for index only access if all of the fields used within
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the query for this file are also key fields for that access path. <p></p>
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Refer
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to <a href="rzajqdta.htm#rzajqdta">Data access on DB2 UDB for iSeries: data access paths and methods</a> for additional tips on optimizing
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a query's join order and index only access.</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 class="section"><p>This message provides the join position of the specified table
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when an index is used to access the table's data. <strong>Join position</strong> pertains
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to the order in which the tables are joined. </p>
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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="pimes.htm" title="You can evaluate the structure and performance of the given SQL statements in a program using informational messages put in the job log by the database manager.">Query optimization performance information messages</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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