mirror of
https://github.com/berkeleydb/libdb.git
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313 lines
12 KiB
HTML
313 lines
12 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>Recovery Procedures</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="filemanagement.html" title="Chapter 5. Managing DB Files" />
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<link rel="prev" href="backuprestore.html" title="Backup Procedures" />
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<link rel="next" href="architectrecovery.html" title="Designing Your Application for Recovery" />
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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 11.2.5.2</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">Recovery Procedures</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="backuprestore.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 5. Managing DB Files</th>
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<td width="20%" align="right"> <a accesskey="n" href="architectrecovery.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"></a>Recovery Procedures</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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<dl>
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<dt>
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<span class="sect2">
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<a href="recovery.html#normalrecovery">Normal Recovery</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="recovery.html#catastrophicrecovery">Catastrophic Recovery</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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DB supports two types of recovery:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p>
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Normal recovery, which is run when your environment is
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opened upon application startup, examines only those
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log records needed to bring the databases to a consistent
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state since the last checkpoint. Normal recovery
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starts with any logs used by any transactions active at
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the time of the last checkpoint, and examines all logs
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from then to the current logs.
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</p>
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</li>
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<li>
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<p>
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Catastrophic recovery, which is performed in the same
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way that normal recovery is except that it examines
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all available log files. You use catastrophic recovery
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to restore your databases from a previously created backup.
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</p>
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</li>
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</ul>
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</div>
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<p>
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Of these two, normal recovery should be considered a routine
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matter; in fact you should run normal
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recovery whenever you start up your application.
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</p>
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<p>
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Catastrophic recovery is run whenever you have lost or
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corrupted your database files and you want to restore from a
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backup. You also run catastrophic recovery when
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you create a hot backup
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(see <a class="xref" href="hotfailover.html" title="Using Hot Failovers">Using Hot Failovers</a> for more information).
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</p>
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<div class="sect2" 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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<h3 class="title"><a id="normalrecovery"></a>Normal Recovery</h3>
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</div>
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</div>
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</div>
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<p>
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Normal recovery examines the contents of your environment's
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log files, and uses this information to ensure that your
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database files are consistent relative to the
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information contained in the log files.
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</p>
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<p>
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Normal recovery also recreates your environment's region files.
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This has the desired effect of clearing any unreleased locks
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that your application may have held at the time of an
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unclean application shutdown.
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</p>
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<p>
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Normal recovery is run only against those log files created
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since the time of your last checkpoint. For this reason,
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your recovery time is dependent on how much data has been
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written since the last checkpoint, and therefore on how
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much log file information there is to examine. If you run
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checkpoints infrequently, then normal recovery can
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take a relatively long time.
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</p>
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<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
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<h3 class="title">Note</h3>
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<p>
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You should run normal recovery every
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time you perform application startup.
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</p>
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</div>
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<p>
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To run normal recovery:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p>
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Make sure all your environment handles are closed.
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</p>
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</li>
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<li>
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<p>
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Normal recovery <span class="emphasis"><em>must
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be</em></span> single-threaded.
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</p>
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</li>
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<li>
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<p>
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Specify <code class="literal">true</code> to
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<code class="methodname">EnvironmentConfig.setRunRecovery()</code>
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when you open your environment.
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</p>
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</li>
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</ul>
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</div>
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<p>
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You can also run recovery by pausing or shutting down your
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application and using the <span class="command"><strong>db_recover</strong></span>
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command line utility.
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</p>
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<p>
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For example:
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</p>
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<pre class="programlisting">package db.txn;
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import com.sleepycat.db.DatabaseException;
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import com.sleepycat.db.Environment;
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import com.sleepycat.db.EnvironmentConfig;
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import java.io.File;
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import java.io.FileNotFoundException;
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...
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Environment myEnv = null;
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try {
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EnvironmentConfig myEnvConfig = new EnvironmentConfig();
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myEnvConfig.setInitializeCache(true);
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myEnvConfig.setInitializeLocking(true);
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myEnvConfig.setInitializeLogging(true);
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myEnvConfig.setTransactional(true);
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// Run normal recovery
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myEnvConfig.setRunRecovery(true);
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myEnv = new Environment(new File("/my/env/home"),
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myEnvConfig);
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// All other operations are identical from here. Notice, however,
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// that we have not created any other threads of control before
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// recovery is complete. You want to run recovery for
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// the first thread in your application that opens an environment,
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// but not for any subsequent threads.
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} catch (DatabaseException de) {
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// Exception handling goes here
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} catch (FileNotFoundException fnfe) {
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// Exception handling goes here
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}</pre>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="catastrophicrecovery"></a>Catastrophic Recovery</h3>
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</div>
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</div>
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</div>
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<p>
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Use catastrophic recovery when you are
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recovering your databases from a previously created backup.
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Note that to restore your databases from a previous backup, you
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should copy the backup to a new environment directory, and
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then run catastrophic recovery. Failure to do so can lead to
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the internal database structures being out of sync with your log files.
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</p>
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<p>
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Catastrophic recovery must be run single-threaded.
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</p>
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<p>
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To run catastrophic recovery:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p>
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Shutdown all database operations.
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</p>
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</li>
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<li>
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<p>
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Restore the backup to an empty directory.
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</p>
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</li>
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<li>
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<p>
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Specify <code class="literal">true</code> to
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<code class="methodname">EnvironmentConfig.setRunRecoveryFatal()</code>
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when you open your environment. This environment
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open must be single-threaded.
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</p>
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</li>
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</ul>
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</div>
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<p>
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You can also run recovery by pausing or shutting down your
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application and using the <span class="command"><strong>db_recover</strong></span>
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command line utility with the the <code class="literal">-c</code> option.
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</p>
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<p>
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Note that catastrophic recovery examines every available
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log file — not just those log files created since the
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last checkpoint as is the case for normal recovery. For this reason,
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catastrophic recovery is likely to take longer than does
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normal recovery.
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</p>
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<p>
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For example:
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</p>
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<pre class="programlisting">package db.txn;
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import com.sleepycat.db.DatabaseException;
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import com.sleepycat.db.Environment;
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import com.sleepycat.db.EnvironmentConfig;
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import java.io.File;
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import java.io.FileNotFoundException;
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...
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Environment myEnv = null;
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try {
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EnvironmentConfig myEnvConfig = new EnvironmentConfig();
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myEnvConfig.setInitializeCache(true);
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myEnvConfig.setInitializeLocking(true);
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myEnvConfig.setInitializeLogging(true);
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myEnvConfig.setTransactional(true);
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// Run catastrophic recovery
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<strong class="userinput"><code>myEnvConfig.setRunFatalRecovery(true);</code></strong>
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myEnv = new Environment(new File("/my/env/home"),
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myEnvConfig);
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} catch (DatabaseException de) {
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// Exception handling goes here
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} catch (FileNotFoundException fnfe) {
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// Exception handling goes here
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}</pre>
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</div>
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</div>
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|||
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<div class="navfooter">
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|||
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<hr />
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|||
|
|
<table width="100%" summary="Navigation footer">
|
|||
|
|
<tr>
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|||
|
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<td width="40%" align="left"><a accesskey="p" href="backuprestore.html">Prev</a> </td>
|
|||
|
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<td width="20%" align="center">
|
|||
|
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<a accesskey="u" href="filemanagement.html">Up</a>
|
|||
|
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</td>
|
|||
|
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<td width="40%" align="right"> <a accesskey="n" href="architectrecovery.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">Backup Procedures </td>
|
|||
|
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<td width="20%" align="center">
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|||
|
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<a accesskey="h" href="index.html">Home</a>
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|||
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</td>
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|||
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<td width="40%" align="right" valign="top"> Designing Your Application for Recovery</td>
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|||
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</tr>
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|||
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</table>
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|||
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</div>
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</body>
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|||
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</html>
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