111 lines
6.3 KiB
HTML
111 lines
6.3 KiB
HTML
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<title>CPI4321 - Access path built for &18 &19</title>
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</head>
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<body id="cpi4321"><a name="cpi4321"><!-- --></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">CPI4321 - Access path built for &18 &19</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">CPI4321</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 ">Access path built for &18 &19.</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 ">A temporary access path was built to access records from member &6
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of &18 &19 in library &5 for reason code &10. This process
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took &11 minutes and &12 seconds. The access path built contains &15
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entries. The access path was built using &16 parallel tasks. A zero for
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the number of parallel tasks indicates that parallelism was not used. The
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reason codes and their meanings follow: <ol><li>Perform specified ordering/grouping criteria.</li>
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<li>Perform specified join criteria.</li>
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<li>Perform specified record selection to minimize I/O wait time.</li>
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</ol>
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<p>The access path was built using the following key fields. The key
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fields and their corresponding sequence (ASCEND or DESCEND) will be shown:
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</p>
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&17. <p></p>
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A key field of *MAP indicates the key
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field is an expression (derived field). <p></p>
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The access path was
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built using sequence table &13 in library &14. <p></p>
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A sequence
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table of *N indicates the access path was built without a sequence table.
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A sequence table of *I indicates the table was an internally derived table
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that is not available to the user. <p></p>
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If &18 &19 in library &5
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is a logical file then the access path is built over member &9 of physical
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file &7 in library &8. <p></p>
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A file name starting with *QUERY
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or *N indicates the access path was built over a temporary file.</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 ">If this query is run frequently, you may want to create an access path
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(index) similar to this definition for performance reasons. Create the access
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path using sequence table &13 in library &14, unless the sequence
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table is *N. If an access path is created, it is possible the query optimizer
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may still choose to create a temporary access path to process the query.
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<p></p>
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If *MAP is returned for one of the key fields or *I is returned
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for the sequence table, then a permanent access path cannot be created. A
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permanent access path cannot be built with these specifications.</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 indicates that a temporary index was created to process
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the query. The new index is created by reading all of the rows in the specified
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table.</p>
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</div>
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<div class="section"><p>The time required to create an index on each run of a query can
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be significant. Consider creating a logical file (<span class="cmdname">CRTLF</span>)
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or an SQL index (CREATE INDEX SQL statement): </p>
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<ul><li>Over the table named in the message help.</li>
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<li>With key columns named in the message help.</li>
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<li>With the ascending or descending sequencing specified in the message help.</li>
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<li>With the sort sequence table specified in the message help.</li>
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</ul>
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</div>
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<div class="section"><p>Consider creating the logical file with select or omit criteria
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that either match or partially match the query's predicates involving constants.
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The database manager will consider using select or omit logical files even
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though they are not explicitly specified on the query.</p>
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</div>
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<div class="section"><p>For certain queries, the optimizer may decide to create an index
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even when an existing one can be used. This might occur when a query has an
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ordering column as a key column for an index, and the only row selection specified
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uses a different column. If the row selection results in roughly 20% of the
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rows or more to be returned, then the optimizer may create a new index to
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get faster performance when accessing the data. The new index minimizes the
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amount of data that needs to be read.</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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