66 lines
3.9 KiB
HTML
66 lines
3.9 KiB
HTML
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<meta name="DC.Title" content="Using MQTs during Query optimization" />
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<meta name="abstract" content="Before using MQTs, you need to consider your environment attributes." />
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<meta name="description" content="Before using MQTs, you need to consider your environment attributes." />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Using MQTs during Query optimization</title>
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</head>
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<body id="rzajqmqtusing"><a name="rzajqmqtusing"><!-- --></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">Using MQTs during Query optimization</h1>
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<div><p>Before using MQTs, you need to consider your environment attributes.</p>
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<div class="section"><p>To even consider using MQTs during optimization the following
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environmental attributes must be true:</p>
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</div>
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<div class="section"> <ul><li>The query must specify ALWCPYDTA(*OPTMIZE) or INSENSITIVE cursor. </li>
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<li>The query must not be a SENSITIVE cursor. </li>
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<li>The table to be replaced with a MQT must not be update or delete capable
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for this query. </li>
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<li>The MQT currently has the ENABLE QUERY OPTIMIZATION attribute active </li>
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<li>The MATERIALIZED_QUERY_TABLE_USAGE QAQQINI option must be set to *ALL
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or *USER to enable use of MQTs. The default setting of MATERIALIZED_QUERY_TABLE_USAGE
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does not allow usage of MQTs. </li>
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<li>The timestamp of the last REFRESH TABLE for a MQT is within the duration
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specified by the MATERIALIZED_QUERY_TABLE_REFRESH_AGE QAQQINI option or *ANY
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is specified which allows MQTs to be considered regardless of the last REFRESH
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TABLE. The default setting of MATERIALIZED_QUERY_TABLE_REFRESH_AGE does not
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allow usage of MQTs. </li>
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<li>The query must be capable of being run through SQE. </li>
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<li>The following QAQQINI options must match: IGNORE_LIKE_REDUNDANT_SHIFTS,
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NORMALIZE_DATA, and VARIABLE_LENGTH_OPTIMIZATION. These options are stored
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at CREATE materialized query table time and must match the options specified
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at query run time. </li>
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<li>The commit level of the MQT must be greater than or equal to the query
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commit level. The commit level of the MQT is either specified in the MQT
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query using the WITH clause or it is defaulted to the commit level that the
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MQT was run under when it was created.</li>
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</ul>
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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="rzajqmqt.htm" title="Materialized query tables (MQTs) (also referred to as automatic summary tables or materialized views) can provide performance enhancements for queries.">Materialized query table optimization</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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