Import BSDDB 4.7.25 (as of svn r89086)
This commit is contained in:
Zachary Ware
246
docs/gsg/JAVA/EnvProps.html
Normal file
246
docs/gsg/JAVA/EnvProps.html
Normal file
@@ -0,0 +1,246 @@
|
||||
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
|
||||
<!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">
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
|
||||
<title>Environment Properties</title>
|
||||
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.62.4" />
|
||||
<link rel="home" href="index.html" title="Getting Started with Berkeley DB" />
|
||||
<link rel="up" href="Env.html" title="Chapter 2. Database Environments" />
|
||||
<link rel="previous" href="EnvClose.html" title="Closing Database Environments" />
|
||||
<link rel="next" href="dpl.html" title="Part I. Programming with the Direct Persistence Layer" />
|
||||
</head>
|
||||
<body>
|
||||
<div class="navheader">
|
||||
<table width="100%" summary="Navigation header">
|
||||
<tr>
|
||||
<th colspan="3" align="center">Environment Properties</th>
|
||||
</tr>
|
||||
<tr>
|
||||
<td width="20%" align="left"><a accesskey="p" href="EnvClose.html">Prev</a> </td>
|
||||
<th width="60%" align="center">Chapter 2. Database Environments</th>
|
||||
<td width="20%" align="right"> <a accesskey="n" href="dpl.html">Next</a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr />
|
||||
</div>
|
||||
<div class="sect1" lang="en" xml:lang="en">
|
||||
<div class="titlepage">
|
||||
<div>
|
||||
<div>
|
||||
<h2 class="title" style="clear: both"><a id="EnvProps"></a>Environment Properties</h2>
|
||||
</div>
|
||||
</div>
|
||||
<div></div>
|
||||
</div>
|
||||
<p>You set properties for the <tt class="classname">Environment</tt> using
|
||||
the <tt class="classname">EnvironmentConfig</tt> class. You can also set properties for a specific
|
||||
<tt class="classname">Environment</tt> instance using <tt class="classname">EnvironmentMutableConfig</tt>.
|
||||
</p>
|
||||
<div class="sect2" lang="en" xml:lang="en">
|
||||
<div class="titlepage">
|
||||
<div>
|
||||
<div>
|
||||
<h3 class="title"><a id="envconfig"></a>The EnvironmentConfig Class</h3>
|
||||
</div>
|
||||
</div>
|
||||
<div></div>
|
||||
</div>
|
||||
<p>
|
||||
The <tt class="classname">EnvironmentConfig</tt> class makes a
|
||||
large number of fields and methods available to you. Describing all of these
|
||||
tuning parameters is beyond the scope of this manual. However, there are a
|
||||
few properties that you are likely to want to set. They are described
|
||||
here.</p>
|
||||
<p>Note that for each of the properties that you can commonly set, there is a
|
||||
corresponding getter method. Also, you can always retrieve the
|
||||
<tt class="classname">EnvironmentConfig</tt> object used by your environment
|
||||
using the <tt class="methodname">Environment.getConfig()</tt> method.
|
||||
</p>
|
||||
<p>
|
||||
You set environment configuration parameters using the following methods on the
|
||||
<tt class="classname">EnvironmentConfig</tt> class:
|
||||
</p>
|
||||
<div class="itemizedlist">
|
||||
<ul type="disc">
|
||||
<li>
|
||||
<p>
|
||||
<tt class="methodname">EnvironmentConfig.setAllowCreate()</tt>
|
||||
</p>
|
||||
<p>If <tt class="literal">true</tt>, the database environment is created
|
||||
when it is opened. If <tt class="literal">false</tt>, environment open fails if the environment
|
||||
does not exist. This property has no meaning if the database
|
||||
environment already exists. Default is <tt class="literal">false</tt>.</p>
|
||||
</li>
|
||||
<li>
|
||||
<p>
|
||||
<tt class="methodname">EnvironmentConfig.setReadOnly()</tt>
|
||||
</p>
|
||||
<p>If <tt class="literal">true</tt>, then all databases opened in this
|
||||
environment must be opened as read-only. If you are writing a
|
||||
multi-process application, then all but one of your processes must set
|
||||
this value to <tt class="literal">true</tt>. Default is <tt class="literal">false</tt>.</p>
|
||||
</li>
|
||||
<li>
|
||||
<p>
|
||||
<tt class="methodname">EnvironmentConfig.setTransactional()</tt>
|
||||
</p>
|
||||
<p>If <tt class="literal">true</tt>, configures the database environment
|
||||
to support transactions. Default is <tt class="literal">false</tt>.</p>
|
||||
</li>
|
||||
</ul>
|
||||
</div>
|
||||
<p>For example:</p>
|
||||
<pre class="programlisting">package db.gettingStarted;
|
||||
|
||||
import com.sleepycat.db.DatabaseException;
|
||||
import com.sleepycat.db.Environment;
|
||||
import com.sleepycat.db.EnvironmentConfig;
|
||||
|
||||
import java.io.File;
|
||||
import java.io.FileNotFoundException;
|
||||
|
||||
...
|
||||
|
||||
Environment myDatabaseEnvironment = null;
|
||||
try {
|
||||
EnvironmentConfig envConfig = new EnvironmentConfig();
|
||||
envConfig.setAllowCreate(true);
|
||||
envConfig.setTransactional(true);
|
||||
myDatabaseEnvironment =
|
||||
new Environment(new File("/export/dbEnv"), envConfig);
|
||||
} catch (DatabaseException dbe) {
|
||||
System.err.println(dbe.toString());
|
||||
System.exit(1);
|
||||
} catch (FileNotFoundException fnfe) {
|
||||
System.err.println(fnfe.toString());
|
||||
System.exit(-1);
|
||||
} </pre>
|
||||
</div>
|
||||
<div class="sect2" lang="en" xml:lang="en">
|
||||
<div class="titlepage">
|
||||
<div>
|
||||
<div>
|
||||
<h3 class="title"><a id="envhandleconfig"></a>EnvironmentMutableConfig</h3>
|
||||
</div>
|
||||
</div>
|
||||
<div></div>
|
||||
</div>
|
||||
<p>
|
||||
<tt class="classname">EnvironmentMutableConfig</tt> manages properties that can be reset after the
|
||||
<tt class="classname">Environment</tt> object has been constructed. In addition, <tt class="classname">EnvironmentConfig</tt>
|
||||
extends <tt class="classname">EnvironmentMutableConfig</tt>, so you can set these mutable properties at
|
||||
<tt class="classname">Environment</tt> construction time if necessary.
|
||||
</p>
|
||||
<p>
|
||||
The <tt class="classname">EnvironmentMutableConfig</tt> class allows you to set the following
|
||||
properties:
|
||||
</p>
|
||||
<div class="itemizedlist">
|
||||
<ul type="disc">
|
||||
<li>
|
||||
<p>
|
||||
<tt class="literal">setCachePercent()</tt>
|
||||
</p>
|
||||
<p>
|
||||
Determines the percentage of JVM memory available to the DB cache.
|
||||
See <a href="cachesize.html">Selecting the Cache Size</a>
|
||||
for more information.
|
||||
</p>
|
||||
</li>
|
||||
<li>
|
||||
<p>
|
||||
<tt class="literal">setCacheSize()</tt>
|
||||
</p>
|
||||
<p>
|
||||
Determines the total amount of memory available to the database cache.
|
||||
See <a href="cachesize.html">Selecting the Cache Size</a>
|
||||
for more information.
|
||||
</p>
|
||||
</li>
|
||||
<li>
|
||||
<p>
|
||||
<tt class="literal">setTxnNoSync()</tt>
|
||||
</p>
|
||||
<p>
|
||||
Determines whether change records created due to a transaction commit are written to the backing
|
||||
log files on disk. A value of <tt class="literal">true</tt> causes
|
||||
the data to not be flushed to
|
||||
disk. See the
|
||||
|
||||
<i class="citetitle">Getting Started with Transaction Processing for Java</i>
|
||||
guide for more information.
|
||||
</p>
|
||||
</li>
|
||||
<li>
|
||||
<p>
|
||||
<tt class="literal">setTxnWriteNoSync()</tt>
|
||||
</p>
|
||||
<p>
|
||||
Determines whether logs are flushed on transaction commit (the logs are still written, however).
|
||||
By setting this value to <tt class="literal">true</tt>, you potentially gain better performance than if
|
||||
you flush the logs on commit, but you do so by losing some of your transaction durability guarantees.
|
||||
See the
|
||||
|
||||
<i class="citetitle">Getting Started with Transaction Processing for Java</i>
|
||||
guide for more information.
|
||||
</p>
|
||||
</li>
|
||||
</ul>
|
||||
</div>
|
||||
<p>
|
||||
There is also a corresponding getter method (<tt class="methodname">getTxnNoSync()</tt>).
|
||||
Moreover, you can always retrieve your environment's
|
||||
<tt class="classname">EnvironmentMutableConfig</tt> object by
|
||||
using the <tt class="methodname">Environment.getMutableConfig()</tt> method.
|
||||
</p>
|
||||
<p>
|
||||
For example:
|
||||
</p>
|
||||
<pre class="programlisting">package db.gettingStarted;
|
||||
|
||||
import com.sleepycat.db.DatabaseException;
|
||||
import com.sleepycat.db.Environment;
|
||||
import com.sleepycat.db.EnvironmentMutableConfig;
|
||||
|
||||
import java.io.File;
|
||||
import java.io.FileNotFoundException;
|
||||
|
||||
|
||||
...
|
||||
|
||||
try {
|
||||
Environment myEnv = new Environment(new File("/export/dbEnv"), null);
|
||||
EnvironmentMutableConfig envMutableConfig =
|
||||
new EnvironmentMutableConfig();
|
||||
envMutableConfig.setTxnNoSync(true);
|
||||
myEnv.setMutableConfig(envMutableConfig);
|
||||
} catch (DatabaseException dbe) {
|
||||
// Exception handling goes here
|
||||
} catch (FileNotFoundException fnfe) {
|
||||
// Exception handling goes here
|
||||
}</pre>
|
||||
</div>
|
||||
</div>
|
||||
<div class="navfooter">
|
||||
<hr />
|
||||
<table width="100%" summary="Navigation footer">
|
||||
<tr>
|
||||
<td width="40%" align="left"><a accesskey="p" href="EnvClose.html">Prev</a> </td>
|
||||
<td width="20%" align="center">
|
||||
<a accesskey="u" href="Env.html">Up</a>
|
||||
</td>
|
||||
<td width="40%" align="right"> <a accesskey="n" href="dpl.html">Next</a></td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td width="40%" align="left" valign="top">Closing Database Environments </td>
|
||||
<td width="20%" align="center">
|
||||
<a accesskey="h" href="index.html">Home</a>
|
||||
</td>
|
||||
<td width="40%" align="right" valign="top"> Part I. Programming with the Direct Persistence Layer</td>
|
||||
</tr>
|
||||
</table>
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
Reference in New Issue
Block a user