2011-09-13 17:44:24 +00:00
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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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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>Recoverability</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 Transaction Processing" />
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<link rel="up" href="introduction.html" title="Chapter 1. Introduction" />
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<link rel="prev" href="multithread-intro.html" title="Multi-threaded and Multi-process Applications" />
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<link rel="next" href="perftune-intro.html" title="Performance Tuning" />
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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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2012-11-14 21:35:20 +00:00
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<p>Library Version 11.2.5.3</p>
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2011-09-13 17:44:24 +00:00
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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">Recoverability</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="multithread-intro.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 1. Introduction</th>
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<td width="20%" align="right"> <a accesskey="n" href="perftune-intro.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="recovery-intro"></a>Recoverability</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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An important part of DB's transactional guarantees is durability.
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<span class="emphasis"><em>Durability</em></span> means that once a
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transaction has been committed, the database modifications performed
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under its protection will not be lost due to system failure.
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</p>
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<p>
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In order to provide the transactional durability guarantee,
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DB uses a write-ahead logging system. Every operation performed on
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your databases is described in a log before it is performed on
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your databases. This is done in order to ensure that an operation can be
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recovered in the event of an untimely application
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or system failure.
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</p>
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<p>
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<span>
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Beyond logging, another important aspect of durability is
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recoverability. That is, backup and restore. </span>
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DB supports a normal recovery that runs against a subset of
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your log files. This is a routine procedure used whenever your
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environment is first opened upon application startup, and it is intended to
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ensure that your database is in a consistent state. DB also
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supports archival backup and recovery in the case of
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catastrophic failure, such as the loss of a physical disk
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drive.
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</p>
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<p>
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This book describes several different backup procedures
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you can use to protect your on-disk data. These procedures
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range from simple offline backup strategies to hot failovers. Hot failovers
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provide not only a backup mechanism, but
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also a way to recover from a fatal hardware failure.
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</p>
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<p>
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This book also describes the recovery procedures you should use
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for each of the backup strategies that you might employ.
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</p>
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<p>
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For a detailed description of backup and restore procedures, see
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<span>
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<a class="xref" href="filemanagement.html" title="Chapter 5. Managing DB Files">Managing DB Files</a>.
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</span>
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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="multithread-intro.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="introduction.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="perftune-intro.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">Multi-threaded
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<span>and Multi-process</span>
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Applications </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"> Performance Tuning</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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