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>Multi-threaded and Multi-process Applications</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="apireq.html" title="Application Requirements" />
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<link rel="next" href="recovery-intro.html" title="Recoverability" />
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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">Multi-threaded
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<span xmlns="http://www.w3.org/1999/xhtml">and Multi-process</span>
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Applications</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="apireq.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="recovery-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="multithread-intro"></a>Multi-threaded
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<span>and Multi-process</span>
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Applications</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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DB is designed to support multi-threaded <span>and
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multi-process</span> applications, but their usage means
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you must pay careful attention to issues of concurrency.
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Transactions help your application's concurrency by providing various levels of
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isolation for your threads of control. In addition, DB
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provides mechanisms that allow you to detect and respond to
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deadlocks.
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</p>
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<p>
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<span class="emphasis"><em>Isolation</em></span> means that database modifications made by
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one transaction will not normally be seen by readers from another
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transaction until the first commits its changes. Different threads
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use different transaction handles, so
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this mechanism is normally used to provide isolation between
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database operations performed by different threads.
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</p>
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<p>
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Note that DB supports different isolation levels. For example,
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you can configure your application to see uncommitted reads, which means
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that one transaction can see data that has been modified but not yet
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committed by another transaction. Doing this might mean your
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transaction reads data "dirtied" by another transaction,
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but which subsequently might change before that
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other transaction commits its changes.
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On the other hand, lowering your isolation
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requirements means that your application can experience
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improved throughput due to reduced lock contention.
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</p>
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<p>
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For more information on concurrency, on managing isolation
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levels, and on deadlock detection, see <a class="xref" href="txnconcurrency.html" title="Chapter 4. Concurrency">Concurrency</a>.
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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="apireq.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="recovery-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">Application Requirements </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"> Recoverability</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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