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126 lines
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<title>Monitoring your queries using Start Database Monitor (STRDBMON)</title>
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<img src="./delta.gif" alt="Start of change" /><!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Monitoring your queries using Start Database Monitor (STRDBMON)</h1>
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<div><p><span class="cmdname">Start Database Monitor (STRDBMON)</span> command gathers
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information about a query in real time and stores this information in an output
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table. This information can help you determine whether your system and your
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queries are performing as they should, or whether they need fine tuning. Database
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monitors can generate significant CPU and disk storage overhead when in use.</p>
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<div class="section"><p>You can gather performance information for a specific query, for
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every query on the server, or for a group of queries on the server. When a
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job is monitored by multiple monitors, each monitor is logging rows to a different
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output table. You can identify rows in the output database table by each row's
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unique identification number.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">What kinds of statistics you can gather</h4><p>The database
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monitor provides the same information that is provided with the query optimizer
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debug messages (<span class="cmdname">Start Debug (STRDBG)</span>) and the <span class="cmdname">Print
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SQL information (PRTSQLINF)</span> command. The following is a sampling
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of the additional information that will be gathered by the database monitors: </p>
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<ul><li>System and job name</li>
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<li>SQL statement and sub-select number</li>
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<li>Start and end timestamp</li>
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<li>Estimated processing time</li>
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<li>Total rows in table queried</li>
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<li>Number of rows selected</li>
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<li>Estimated number of rows selected</li>
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<li>Estimated number of joined rows</li>
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<li>Key columns for advised index</li>
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<li>Total optimization time</li>
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<li>Join type and method</li>
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<li>ODP implementation</li>
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</ul>
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</div>
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<div class="section"><h4 class="sectiontitle">How you can use performance statistics</h4><p>You can use
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these performance statistics to generate various reports. For instance, you
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can include reports that show queries that: </p>
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<ul><li>Use an abundance of the server resources.</li>
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<li>Take an extremely long time to execute.</li>
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<li>Did not run because of the query governor time limit.</li>
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<li>Create a temporary index during execution</li>
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<li>Use the query sort during execution</li>
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<li>Might perform faster with the creation of a keyed logical file containing
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keys suggested by the query optimizer.</li>
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</ul>
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<div class="note"><span class="notetitle">Note:</span> A query that is canceled by an end request generally does not generate
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a full set of performance statistics. However, it does contain all the information
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about how a query was optimized, with the exception of runtime or multi-step
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query information.</div>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="strdbmon.htm">Start Database Monitor (STRDBMON) command</a></strong><br />
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The <span class="cmdname">Start Database Monitor (STRDBMON)</span> command
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starts the collection of database performance statistics for a specified
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job, for all jobs on the system or for a selected set of jobs. The statistics
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are placed in a user-specified database table and member. If the table or
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member do not exist, one is created based on the QAQQDBMN table in library
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QSYS. If the table and member do exist, the record format of the specified
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table is verified to insure it is the same.</li>
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<li class="ulchildlink"><strong><a href="endbmon.htm">End Database Monitor (ENDDBMON) command</a></strong><br />
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The <span class="cmdname">End Database Monitor (ENDDBMON)</span> command
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ends the collection of database performance statistics for a specified job,
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all jobs on the system or a selected set of jobs (for example, a generic job
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name).</li>
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<li class="ulchildlink"><strong><a href="dbmonperfrows.htm">Database monitor performance rows</a></strong><br />
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The rows in the database table are uniquely identified by their
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row identification number. The information within the file-based monitor (<span class="cmdname">Start
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Database Monitor (STRDBMON)</span>) is written out based upon
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a set of logical formats which are defined in the Database Monitor formats.
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These views correlate closely to the debug messages and the <span class="cmdname">Print
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SQL Information (PRSQLINF)</span> messages.</li>
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<li class="ulchildlink"><strong><a href="dbmonexamples.htm">Database monitor examples</a></strong><br />
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The iSeries™ navigator
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interface provides a powerful tool for gathering and analyzing performance
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monitor data using database monitor. However, you may want to do your own
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analysis of the database monitor files.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="queryopt.htm" title="Query optimization is an iterative process. You can gather performance information about your queries and control the processing of your queries.">Optimizing query performance using query optimization tools</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../cl/strdbg.htm">Start Debug (STRDBG) command</a></div>
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<div><a href="../cl/prtsqlinf.htm">Print SQL Information (PRTSQLINF) command</a></div>
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<div><a href="../cl/strdbmon.htm">Start Database Monitor (STRDBMON) command</a></div>
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</div>
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</div>
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