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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>Monitoring I/O</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="Monitoring I/O" /> <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_realtime012.htm" title="Previous" type="text/html" /> <link rel="next" href="tdppt_realtime014.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_realtime012.htm"><img src="./dcommon/gifs/leftnav.gif" alt="Previous" /><br /> <span class="icon">Previous</span></a> </td> <td align="center"><a href="tdppt_realtime014.htm"><img src="./dcommon/gifs/rightnav.gif" alt="Next" /><br /> <span class="icon">Next</span></a></td> </tr> </table> <p><a id="CBBIFFJE" name="CBBIFFJE"></a><a id="TDPPT326" name="TDPPT326"></a></p> <div class="sect2"><!-- infolevel="all" infotype="General" --> <h1>Monitoring I/O</h1> <a name="BEGIN" id="BEGIN"></a> <p><a id="sthref132" name="sthref132"></a><a id="sthref133" name="sthref133"></a>The I/O charts show I/O statistics collected from all database clients. The I/O wait time for a database process represents the amount of time that the process could have been doing useful work if a pending I/O had completed. Oracle Database captures the I/O wait times for all important I/O components in a uniform fashion so that every I/O wait by any Oracle process can be deduced from the I/O statistics.</p> <p>The Latency for Synchronous Single Block Reads chart shows the total perceived I/O latency for a block read, which is the time difference between when an I/O is issued and when it is processed by the database. Most systems are performing satisfactorily if latency is fewer than 10 milliseconds. This type of I/O request is the best indicator of I/O performance for the following reasons:</p> <ul> <li> <p>Write operations may exhibit good performance because of write caches in storage.</p> </li> <li> <p>Because multiblock I/O requests have varying sizes, they can take different amounts of time.</p> </li> <li> <p>The latency of asynchronous I/O requests does not represent the full I/O wait time.</p> </li> </ul> <p>The other charts shown depend on your selection for <span class="bold">I/O Breakdown</span>, as described in the following sections:</p> <ul> <li> <p><a href="tdppt_realtime014.htm#CBBEFAAC">Monitoring I/O by Function</a></p> </li> <li> <p><a href="tdppt_realtime015.htm#CBBIHDHB">Monitoring I/O by Type</a></p> </li> <li> <p><a href="tdppt_realtime016.htm#CBBEBAAH">Monitoring I/O by Consumer Group</a></p> </li> </ul> <div class="helpinfonotealso"> <h2>Related Topics</h2> <p><a href="tdppt_realtime011.htm#CHDBEHAG">Monitoring Instance Activity</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. All rights reserved.</span><br /> <a href="./dcommon/html/cpyr.htm"><span class="copyrightlogo">Legal Notices</span></a></td> <td align="center"><a href="tdppt_realtime012.htm"><img src="./dcommon/gifs/leftnav.gif" alt="Previous" /><br /> <span class="icon">Previous</span></a> </td> <td align="center"><a href="tdppt_realtime014.htm"><img src="./dcommon/gifs/rightnav.gif" alt="Next" /><br /> <span class="icon">Next</span></a></td> </tr> </table> </div> <!-- class="footer" --></div> </body> </html>
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