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102 lines
4.6 KiB
HTML
102 lines
4.6 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>Environment Statistics</title>
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<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Getting Started with Berkeley DB Java Edition" />
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<link rel="up" href="env.html" title="Chapter 2. Database Environments" />
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<link rel="prev" href="EnvProps.html" title="Environment Properties" />
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<link rel="next" href="dbenvUsageExample.html" title="Database Environment Management Example" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 12.2.7.5</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Environment Statistics</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="EnvProps.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 2. Database Environments</th>
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<td width="20%" align="right"> <a accesskey="n" href="dbenvUsageExample.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="envStats"></a>Environment Statistics</h2>
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</div>
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</div>
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</div>
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<p>
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JE offers a wealth of information that you can examine regarding your environment's operations. The majority
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of this information involves numbers relevant only to the JE developer and as such a description of those
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statistics is beyond the scope of this manual.
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</p>
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<p>
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However, one statistic that is very important (especially for
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long-running applications) is
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<code class="methodname">EnvironmentStats.getNCacheMiss()</code>.
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This statistic returns the total number of
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requests for database objects that were not serviceable from the cache.
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This number is important to the
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application administrator who is attempting to determine the proper size for the in-memory cache.
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See <a class="xref" href="cachesize.html" title="Sizing the Cache">Sizing the Cache</a> for details.
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</p>
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<p>
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To obtain this statistic from your environment, call <code class="methodname">Environment.getStats()</code> to return
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an <code class="classname">EnvironmentStats</code> object. You can then call the
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<code class="methodname">EnvironmentStats.getNCacheMiss()</code> method. For example:
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</p>
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<a id="je_env5"></a>
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<pre class="programlisting">import com.sleepycat.je.Environment;
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...
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long cacheMisses = myEnv.getStats(null).getNCacheMiss();
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...
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</pre>
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<p>
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Note that <code class="methodname">Environment.getStats()</code> can only obtain statistics from your application's
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process. In order for the application administrator to obtain this statistic, you must either
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use JMX to retrieve the statistic
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(see <a class="xref" href="jmx.html" title="JConsole and JMX Support">JConsole and JMX Support</a>)
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or you must print it for examination (for example, log the value once a minute).
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</p>
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<p>
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Remember that what is really important for cache sizing is the change in this value over time, and not the actual value
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itself. So you might consider offering a delta from one examination of this statistic to the next (a delta of 0 is
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desired while large deltas are an indication that the cache is too small).
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</p>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="EnvProps.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="env.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="dbenvUsageExample.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Environment Properties </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> Database Environment Management Example</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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