Import BSDDB 4.7.25 (as of svn r89086)
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Zachary Ware
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docs/gsg_txn/JAVA/logfileremoval.html
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docs/gsg_txn/JAVA/logfileremoval.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>Removing Log Files</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 V1.62.4" />
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<link rel="home" 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="previous" href="hotfailover.html" title="Using Hot Failovers" />
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<link rel="next" href="logconfig.html" title="Configuring the Logging Subsystem" />
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</head>
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<body>
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<div class="navheader">
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Removing Log Files</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="hotfailover.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="logconfig.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="logfileremoval"></a>Removing Log Files</h2>
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</div>
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</div>
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<div></div>
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</div>
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<p>
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By default DB does not delete log files for you. For this reason,
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DB's log files will eventually grow to consume an
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unnecessarily large amount of disk space. To guard against
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this, you should periodically take administrative action to
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remove log files that are no longer in use by your application.
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</p>
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<p>
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You can remove a log file if all of the following are true:
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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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the log file is not involved in an active transaction.
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</p>
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</li>
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<li>
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<p>
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a checkpoint has been performed
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<span class="emphasis"><em>after</em></span> the log file was
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created.
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</p>
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</li>
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<li>
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<p>
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the log file is not the only log file in the
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environment.
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</p>
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</li>
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<li>
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<p>
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the log file that you want to remove has already been
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included in an offline or hot backup.
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Failure to observe this last condition can cause your
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backups to be unusable.
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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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DB provides several mechanisms to remove log files that
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meet all but the last criteria (DB has no way to know which
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log files have already been included in a backup). The
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following mechanisms make it easy to remove unneeded log files,
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but can result in an unusable backup if the log files are not first
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saved to your archive location. All of the following
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mechanisms automatically delete unneeded log files for you:
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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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Run the <span><b class="command">db_archive</b></span> command line
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utility with the <tt class="literal">-d</tt> option.
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</p>
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</li>
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<li>
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<p>
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From within your application, call the
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<span>
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<tt class="methodname">Environment.removeOldLogFiles()</tt>
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method.
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</span>
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</p>
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</li>
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<li>
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<p>
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<span>
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Specify <tt class="literal">true</tt> to the
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<tt class="methodname">EnvironmentConfig.setLogAutoRemove()</tt>
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method. Note that setting this property affects
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all environment handles opened against the
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environment; not just the handle used to set
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the property.
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</span>
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</p>
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<p>
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Note that unlike the other log removal mechanisms
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identified here, this method actually causes log files
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to be removed on an on-going basis as they become
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unnecessary. This is extremely desirable behavior if
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what you want is to use the absolute minimum amount of
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disk space possible for your application. This
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mechanism <span class="emphasis"><em>will</em></span> leave you with
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the log files that are required to run normal recovery.
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However, it is highly likely that this mechanism will
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prevent you from running catastrophic recovery.
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</p>
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<p>
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Do NOT use this mechanism if you want to be able to
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perform catastrophic recovery, or if you want to be
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able to maintain a hot 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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In order to safely remove log files and still be able to
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perform catastrophic recovery, use the
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<span><b class="command">db_archive</b></span> command line utility as follows:
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</p>
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<div class="orderedlist">
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<ol type="1">
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<li>
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<p>
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Run either a normal or hot backup as described in
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<a href="backuprestore.html">Backup Procedures</a>. Make
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sure that all of this data is safely stored to your
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backup media before continuing.
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</p>
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</li>
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<li>
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<p>
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If you have not already done so, perform a checkpoint.
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See <a href="filemanagement.html#checkpoints">Checkpoints</a>
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for more information.
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</p>
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</li>
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<li>
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<p>
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If you are maintaining a hot backup, perform the hot
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backup procedure as described in
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<a href="hotfailover.html">Using Hot Failovers</a>.
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</p>
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</li>
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<li>
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<p>
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Run the <span><b class="command">db_archive</b></span> command line
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utility with the <tt class="literal">-d</tt> option against
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your production environment.
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</p>
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</li>
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<li>
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<p>
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Run the <span><b class="command">db_archive</b></span> command line
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utility with the <tt class="literal">-d</tt> option against
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your failover environment, if you are maintaining one.
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</p>
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</li>
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</ol>
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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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<tr>
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<td width="40%" align="left"><a accesskey="p" href="hotfailover.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="logconfig.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">Using Hot Failovers </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"> Configuring the Logging Subsystem</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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