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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=us-ascii" /> <meta http-equiv="Content-Style-Type" content="text/css" /> <meta http-equiv="Content-Script-Type" content="text/javascript" /> <title>Gathering Database Statistics Using the Automatic Workload Repository</title> <meta name="generator" content="Oracle DARB XHTML Converter (Mode = ohj/ohw) - Version 5.1.1 Build 005" /> <meta name="date" content="2009-05-27T15:13:1Z" /> <meta name="robots" content="noarchive" /> <meta name="doctitle" content="Gathering Database Statistics Using the Automatic Workload Repository" /> <meta name="relnum" content="11g Release 2 (11.2)" /> <meta name="partnum" content="E10822-01" /> <link rel="copyright" href="./dcommon/html/cpyr.htm" title="Copyright" type="text/html" /> <link rel="stylesheet" href="./dcommon/css/blafdoc.css" title="Oracle BLAFDoc" type="text/css" /> <link rel="contents" href="toc.htm" title="Contents" type="text/html" /> <link rel="prev" href="tdppt_method.htm" title="Previous" type="text/html" /> <link rel="next" href="tdppt_method002.htm" title="Next" type="text/html" /> <script src="./callback.js" type="text/javascript"></script> <noscript>Your browser does not support JavaScript. This help page requires JavaScript to render correctly.</noscript> </head> <body> <div class="zz-skip-header"><a href="#BEGIN">Skip Headers</a></div> <table class="simple oac_no_warn" summary="" cellspacing="0" cellpadding="0" width="100%"> <col width="86%" /> <col width="*" /> <tr valign="bottom"> <td align="left"></td> <td align="center"><a href="tdppt_method.htm"><img src="./dcommon/gifs/leftnav.gif" alt="Previous" /><br /> <span class="icon">Previous</span></a> </td> <td align="center"><a href="tdppt_method002.htm"><img src="./dcommon/gifs/rightnav.gif" alt="Next" /><br /> <span class="icon">Next</span></a></td> </tr> </table> <p><a id="CAEICJEI" name="CAEICJEI"></a><a id="TDPPT007" name="TDPPT007"></a></p> <div class="sect1"><!-- infolevel="all" infotype="General" --> <h1>Gathering Database Statistics Using the Automatic Workload Repository</h1> <a name="BEGIN" id="BEGIN"></a> <p><a id="sthref5" name="sthref5"></a><a id="sthref6" name="sthref6"></a><a id="sthref7" name="sthref7"></a>Database statistics provide information about the type of load on the database and the internal and external resources used by the database. To accurately diagnose performance problems with the database using ADDM, statistics must be available.</p> <p>A <span class="bold">cumulative statistic</span> is a count such as the number of block reads. Oracle Database generates many types of cumulative statistics for the system, sessions, and individual SQL statements. Oracle Database also tracks cumulative statistics about segments and services. <a id="sthref8" name="sthref8"></a>Automatic Workload Repository (AWR) automates database statistics gathering by collecting, processing, and maintaining performance statistics for database problem detection and self-tuning purposes.</p> <p>By default, the database gathers statistics every hour and creates an <span class="bold">AWR snapshot</span>, which is a set of data for a specific time that is used for performance comparisons<a id="sthref9" name="sthref9"></a><a id="sthref10" name="sthref10"></a>. The delta values captured by the snapshot represent the changes for each statistic over the time period. Statistics gathered by AWR are queried from memory. The gathered data can be displayed in both reports and views.</p> <p>The following initialization parameters are relevant for AWR:</p> <ul> <li> <p><code>STATISTICS_LEVEL</code></p> <p>Set this parameter to <code>TYPICAL</code> (default) or <code>ALL</code> to enable statistics gathering by AWR. Setting <code>STATISTICS_LEVEL</code> to <code>BASIC</code> disables many Oracle Database features, including AWR, and is not recommended. To learn more about the <code>STATISTICS_LEVEL</code> parameter, see <a href="javascript:open('http://www.oracle.com/pls/db112/lookup?id=REFRN10214','newWindow').focus()"><span class="italic">Oracle Database Reference</span></a>.</p> </li> <li> <p><code>CONTROL_MANAGEMENT_PACK_ACCESS</code></p> <p>Set to <code>DIAGNOSTIC+TUNING</code> (default) or <code>DIAGNOSTIC</code> to enable automatic database diagnostic monitoring. Setting <code>CONTROL_MANAGEMENT_PACK_ACCESS</code> to <code>NONE</code> disables many Oracle Database features, including ADDM, and is strongly discouraged.</p> </li> </ul> <p>To learn more about these initialization parameters, see <a href="javascript:open('http://www.oracle.com/pls/db112/lookup?id=REFRN10214','newWindow').focus()"><span class="italic">Oracle Database Reference</span></a>.</p> <p><a id="sthref11" name="sthref11"></a><a id="sthref12" name="sthref12"></a>The database statistics collected and processed by AWR include:</p> <ul> <li> <p><a href="tdppt_method002.htm#CIHCACJG">Time Model Statistics</a></p> </li> <li> <p><a href="tdppt_method003.htm#CIHGGECF">Wait Event Statistics</a></p> </li> <li> <p><a href="tdppt_method004.htm#CIHFGGBH">Session and System Statistics</a></p> </li> <li> <p><a href="tdppt_method005.htm#CIHBEFGH">Active Session History Statistics</a></p> </li> <li> <p><a href="tdppt_method006.htm#CIHIEFBG">High-Load SQL Statistics</a></p> </li> </ul> <div class="helpinfonotealso"> <h2>Related Topics</h2> <p><a href="tdppt_method.htm#CIHIEGEC">Oracle Database Performance Method</a></p> </div> <!-- Start Footer --> <div class="footer"> <table class="simple oac_no_warn" summary="" cellspacing="0" cellpadding="0" width="100%"> <col width="86%" /> <col width="*" /> <tr> <td align="left"><span class="copyrightlogo">Copyright © 2007, 2009, Oracle and/or its affiliates. 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