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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 6. Summary and Examples</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="jehotfailover.html" title="Hot Failover" />
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<link rel="next" href="txnexample_java.html" title="Base API Transaction Example" />
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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 6. Summary and Examples</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="jehotfailover.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="txnexample_java.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="wrapup"></a>Chapter 6. Summary and Examples</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="wrapup.html#anatomy">Anatomy of a Transactional Application</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="txnexample_java.html">Base API Transaction Example</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="txnexample_java.html#txnguideexample">TxnGuide.java</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="txnexample_java.html#payloaddata">PayloadData.java</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="txnexample_java.html#dbwriter">DBWriter.java</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="txnexample_dpl.html">DPL Transaction Example</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="txnexample_dpl.html#txnguideexample_dpl">TxnGuide.java</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="txnexample_dpl.html#payloaddataentity">PayloadDataEntity.java</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="txnexample_dpl.html#storewriter">StoreWriter.java</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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</dl>
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</div>
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<p>
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Throughout this manual we have presented the concepts and
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mechanisms that you need to provide transactional protection for
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your application. In this chapter, we summarize these
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mechanisms, and we provide a complete example of a multi-threaded
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transactional JE application.
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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="anatomy"></a>Anatomy of a Transactional 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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Transactional applications are characterized by performing the
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following activities:
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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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Create your environment handle.
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</p>
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</li>
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<li>
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<p>
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Open your environment, specifying that the transactional subsystem is to be used.
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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 using the base API, open your database handles, indicating that they are to support transactions.
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Otherwise, open your store such that it is configured for transactions.
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</p>
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</li>
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<li>
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<p>
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Spawn off worker threads. How many of these you need and
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how they split their JE workload is entirely up to your
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application's requirements. However, any worker threads
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that perform write operations will do the following:
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</p>
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<div class="orderedlist">
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<ol type="a">
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<li>
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<p>
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Begin a 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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Perform one or more read and write
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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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Commit the transaction if all goes well.
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</p>
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</li>
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<li>
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<p>
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Abort and retry the operation if a deadlock is
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detected.
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</p>
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</li>
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<li>
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<p>
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Abort the transaction for most other errors.
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</p>
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</li>
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</ol>
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</div>
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</li>
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<li>
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<p>
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On application shutdown:
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</p>
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<div class="orderedlist">
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<ol type="a">
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<li>
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<p>
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Make sure there are no opened cursors.
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</p>
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</li>
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<li>
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<p>
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Make sure there are no active transactions. Either
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abort or commit all transactions before shutting
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down.
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</p>
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</li>
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<li>
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<p>
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Close your databases.
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</p>
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</li>
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<li>
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<p>
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Close your environment.
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</p>
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</li>
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</ol>
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</div>
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</li>
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</ol>
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</div>
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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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Robust JE applications should monitor their worker threads to
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make sure they have not died unexpectedly. If a thread does
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terminate abnormally, you must shutdown all your worker threads
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and then run normal recovery (you will have to reopen your
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environment to do this). This is the only way to clear any
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resources (such as a lock or a mutex) that the abnormally
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exiting worker thread might have been holding at the time that
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it died.
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</p>
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<p>
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Failure to perform this recovery can cause your
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still-functioning worker threads to eventually block forever
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while waiting for a lock that will never be released.
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</p>
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</div>
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<p>
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In addition to these activities, which are entirely handled by code
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within your application, you also need to periodically back up your
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log files. This is required in order to obtain the durability
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guarantee made by JE's transaction ACID support. See
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<a class="xref" href="jebackuprestore.html" title="Chapter 5. Backing up and Restoring Berkeley DB, Java Edition Applications">Backing up and Restoring Berkeley DB, Java Edition Applications</a>
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for more information.
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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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||
<tr>
|
||
<td width="40%" align="left"><a accesskey="p" href="jehotfailover.html">Prev</a> </td>
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||
<td width="20%" align="center"> </td>
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||
<td width="40%" align="right"> <a accesskey="n" href="txnexample_java.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">Hot Failover </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"> Base API Transaction Example</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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