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112 lines
5 KiB
HTML
112 lines
5 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>Backing up a Replicated Application</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 High Availability Applications" />
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<link rel="up" href="utilities.html" title="Chapter 4. Utilities" />
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<link rel="prev" href="logfile-restore.html" title="Restoring Log Files" />
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<link rel="next" href="enablerep.html" title="Converting Existing Environments for Replication" />
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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">Backing up a Replicated Application</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="logfile-restore.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 4. Utilities</th>
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<td width="20%" align="right"> <a accesskey="n" href="enablerep.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="dbbackup"></a>Backing up a Replicated Application</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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In a stand-alone, non-replicated JE application, the log is
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strictly append only. You use the <a class="ulink" href="../java/com/sleepycat/je/util/DbBackup.html" target="_top">DbBackup</a> class to help
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applications coordinate while database operations are
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continuing to add to the log. This helper class does this by
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defining the log files needed for a consistent backup, and then freezes
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all changes to those files, including any changes that might be
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made by JE background operations. The application can copy
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that defined set of files and finish operation without checking
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for the ongoing creation of new files. Also, there will be no
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need to check for a newer version of the last file on the next
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backup.
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</p>
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<p>
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When you are using JE HA, however, log files other than the
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last log file might be modified as part of the HA sync-up
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operation. Though a rare occurrence, such
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modifications would invalidate the backup because there is the
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chance that files are modified after being copied.
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</p>
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<p>
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If this happens, <a class="ulink" href="../java/com/sleepycat/je/util/DbBackup.html#endBackup()" target="_top">DbBackup.endBackup()</a> throws a
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<a class="ulink" href="../java/com/sleepycat/je/rep/LogOverwriteException.html" target="_top">LogOverwriteException</a>. Upon encountering this exception, the
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backup files should be discarded and a new set of backup files
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created.
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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"> for (int i=0; i < BACKUP_RETRIES; i++) {
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final ReplicatedEnvironment repEnv = ...;
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final DbBackup backupHelper = new DbBackup(repEnv);
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backupHelper.startBackup();
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String[] filesForBackup =
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backupHelper.getLogFilesInBackupSet();
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/* Copy the files to archival storage. */
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myApplicationCopyMethod(filesForBackup);
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try {
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backupHelper.endBackup();
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break;
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} catch (LogOverwriteException e) {
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/* Remove backed up files. */
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myApplicationCleanupMethod();
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continue;
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} finally {
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repEnv.close();
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}
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} </pre>
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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="logfile-restore.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="utilities.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="enablerep.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">Restoring Log Files </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"> Converting Existing Environments for Replication</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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