120 lines
6.8 KiB
HTML
120 lines
6.8 KiB
HTML
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<meta name="DC.Title" content="CPI432A - Query optimizer timed out for file &1" />
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<title>CPI432A - Query optimizer timed out for file &1</title>
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</head>
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<body id="cpi432a"><a name="cpi432a"><!-- --></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">CPI432A - Query optimizer timed out for file &1</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="d0e19">CPI432A</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="d0e19 ">Message Text:</td>
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<td valign="middle" width="73.9795918367347%" headers="d0e19 ">Query optimizer timed out for file &1.</td>
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</tr>
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<tr valign="middle"><td valign="middle" width="26.02040816326531%" headers="d0e19 ">Cause Text:</td>
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<td valign="middle" width="73.9795918367347%" headers="d0e19 ">The query optimizer timed out before it could consider all access paths
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built over member &3 of file &1 in library &2. <p></p>
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The list
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below shows the access paths considered before the optimizer timed out. If
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file &1 in library &2 is a logical file then the access paths specified
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are actually built over member &9 of physical file &7 in library &8.
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<p></p>
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Following each access path name in the list is a reason code
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which explains why the access path was not used. A reason code of 0 indicates
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that the access path was used to implement the query. <p></p>
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The
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reason codes and their meanings follow: <ol><li>Access path was not in a valid state. The system invalidated the access
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path.</li>
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<li>Access path was not in a valid state. The user requested that the access
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path be rebuilt.</li>
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<li>Access path is a temporary access path (resides in library QTEMP) and
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was not specified as the file to be queried.</li>
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<li>The cost to use this access path, as determined by the optimizer, was
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higher than the cost associated with the chosen access method.</li>
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<li>The keys of the access path did not match the fields specified for the
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ordering/grouping criteria.</li>
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<li>The keys of the access path did not match the fields specified for the
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join criteria.</li>
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<li>Use of this access path would not minimize delays when reading records
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from the file as the user requested.</li>
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<li>The access path cannot be used for a secondary file of the join query
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because it contains static select/omit selection criteria. The join-type of
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the query does not allow the use of select/omit access paths for secondary
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files.</li>
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<li>File &1 contains record ID selection. The join-type of the query forces
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a temporary access path to be built to process the record ID selection.</li>
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<li> and greater - View the second level message text of the next message
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issued (CPI432D) for an explanation of these reason codes.</li>
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</ol>
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</td>
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</tr>
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<tr valign="middle"><td valign="middle" width="26.02040816326531%" headers="d0e19 ">Recovery Text:</td>
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<td valign="middle" width="73.9795918367347%" headers="d0e19 ">To ensure an access path is considered for optimization specify that
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access path to be the queried file. The optimizer will first consider the
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access path of the file specified on the query. SQL-created indexes cannot
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be queried but can be deleted and recreated to increase the chance they will
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be considered during query optimization. <p></p>
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The user may want to delete
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any access paths no longer needed.</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>The optimizer stops considering indexes when the time spent optimizing
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the query exceeds an internal value that corresponds to the estimated time
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to run the query and the number of rows in the queried tables. Generally,
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the more rows in the tables, the greater the number of indexes that will be
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considered.</p>
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</div>
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<div class="section"><p>When the estimated time to run the query is exceeded, the optimizer
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does not consider any more indexes and uses the current best method to implement
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the query. Either an index has been found to get the best performance, or
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an index will have to be created. If the actual time to execute the query
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exceeds the estimated run time this may indicate the optimizer did not consider
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the best index.</p>
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</div>
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<div class="section"><p>The message help contains a list of indexes that were considered
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before the optimizer timed out. By viewing this list of indexes, you may be
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able to determine if the optimizer timed out before the best index was considered.</p>
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</div>
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<div class="section"><p>To ensure that an index is considered for optimization, specify
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the logical file associated with the index as the table to be queried. The
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optimizer will consider the index of the table specified on the query or SQL
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statement first. Remember that SQL indexes cannot be queried.</p>
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</div>
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<div class="section"><p>You may want to delete any indexes that are no longer needed.</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 class="relref"><strong>Related reference</strong><br />
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<div><a href="cpi432d.htm">CPI432D - Additional access path reason codes were used</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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