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HTML
172 lines
7.8 KiB
HTML
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<?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>Chapter 5. Backing up and Restoring Berkeley DB, Java Edition Applications</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 Transaction Processing" />
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<link rel="up" href="index.html" title="Getting Started with Berkeley DB, Java Edition Transaction Processing" />
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<link rel="prev" href="readmodifywrite.html" title="Read/Modify/Write" />
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<link rel="next" href="chkpoint.html" title="Checkpoints" />
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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">Chapter 5. Backing up and Restoring Berkeley DB, Java Edition Applications</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="readmodifywrite.html">Prev</a> </td>
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<th width="60%" align="center"> </th>
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<td width="20%" align="right"> <a accesskey="n" href="chkpoint.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="chapter" 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"><a id="jebackuprestore"></a>Chapter 5. Backing up and Restoring Berkeley DB, Java Edition Applications</h2>
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</div>
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</div>
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</div>
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<div class="toc">
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<p>
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<b>Table of Contents</b>
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</p>
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<dl>
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<dt>
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<span class="sect1">
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<a href="jebackuprestore.html#datamod">Normal Recovery</a>
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</span>
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</dt>
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<dt>
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<span class="sect1">
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<a href="chkpoint.html">Checkpoints</a>
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</span>
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</dt>
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<dt>
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<span class="sect1">
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<a href="backup.html">Performing Backups</a>
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</span>
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</dt>
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<dd>
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<dl>
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<dt>
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<span class="sect2">
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<a href="backup.html#partialBackup">Performing a Hot Backup</a>
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</span>
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</dt>
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<dt>
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<span class="sect2">
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<a href="backup.html#completeBackup">Performing an Offline Backup</a>
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</span>
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</dt>
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<dt>
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<span class="sect2">
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<a href="backup.html#dbbackuphelper">Using the DbBackup Helper Class</a>
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</span>
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</dt>
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</dl>
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</dd>
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<dt>
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<span class="sect1">
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<a href="jecatastrophicrecovery.html">Performing Catastrophic Recovery</a>
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</span>
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</dt>
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<dt>
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<span class="sect1">
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<a href="jehotfailover.html">Hot Failover</a>
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</span>
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</dt>
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</dl>
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</div>
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<p>
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Fundamentally, you backup your databases by copying JE log
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files off to a safe storage location. To restore your database from
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a backup, you copy those files to an appropriate directory on disk
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and restart your JE application.
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</p>
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<p>
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Note that if you are using subdirectories to store your JE log
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files, then your backup and restore process must maintain the
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relationship between each log file and the subdirectory in which
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JE intially placed it. That is, if JE placed log file
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number 17 in the subdirectory named <code class="literal">data003</code>,
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then when you perform a recovery log file number 17 must be placed
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inside subdirectory <code class="literal">data003</code>.
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</p>
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<p>
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Beyond these simple activities, there are some differing backup strategies that you may want to consider. These
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topics are described in this chapter.
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</p>
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<p>
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Before continuing, before you review the information on log files and background threads in the
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<em class="citetitle">Getting Started with Berkeley DB, Java Edition</em> guide. Those topics contain important
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information that is basic to the following discussion on backups and restores.
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</p>
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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="datamod"></a>Normal Recovery</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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Remember that internally JE databases are organized in a BTree, and that in order to operate JE
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requires the complete BTree be available to it.
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</p>
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<p>
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When database records are created, modified, or deleted, the modifications are represented in the BTree's
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leaf nodes. Beyond leaf node changes, database record modifications can also cause changes to other BTree
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nodes and structures.
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</p>
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<p>
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Now, if your writes are transaction-protected, then every time a transaction is committed the leaf nodes
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(and <span class="emphasis"><em>only</em></span> the leaf nodes) modified by that transaction are written to the JE log
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files on disk. Also, remember that the durability of the write (whether a flush or fsync is
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performed) depends on the type of commit that is requested. See <a class="xref" href="nodurabletxn.html" title="Non-Durable Transactions">Non-Durable Transactions</a> for more information.
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</p>
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<p>
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Normal recovery, then, is the process of recreating the entire BTree from the information available in the
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leaf nodes. You do not have to do anything special to cause normal recovery to be run; this occurs every
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time a JE environment is opened.
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</p>
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<p>
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You can know if normal recovery must be run by catching <a class="ulink" href="../java/com/sleepycat/je/EnvironmentFailureException.html" target="_top">EnvironmentFailureException</a>.
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This exception indicates that a failure has occurred that impacts the
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Environment as a whole. Upon seeing this exception, you should run
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<a class="ulink" href="../java/com/sleepycat/je/Environment.html#isValid--" target="_top">Environment.isValid()</a>. If it returns <code class="literal">true</code>,
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then you can continue operating without any further action. However, if it
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returns <code class="literal">false</code>, then you must close and reopen all
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<a class="ulink" href="../java/com/sleepycat/je/Environment.html" target="_top">Environment</a> handles so that normal recovery can be run.
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</p>
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</div>
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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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|
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<tr>
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|||
|
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<td width="40%" align="left"><a accesskey="p" href="readmodifywrite.html">Prev</a> </td>
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|||
|
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<td width="20%" align="center"> </td>
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<td width="40%" align="right"> <a accesskey="n" href="chkpoint.html">Next</a></td>
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|||
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Read/Modify/Write </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"> Checkpoints</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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