2011-09-13 17:44:24 +00:00
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>The Replication APIs</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 Replicated Berkeley DB Applications" />
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<link rel="up" href="introduction.html" title="Chapter 1. Introduction" />
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<link rel="prev" href="repadvantage.html" title="Replication Benefits" />
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<link rel="next" href="elections.html" title="Holding Elections" />
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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">The Replication APIs</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="repadvantage.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="elections.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="apioverview"></a>The Replication APIs</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="apioverview.html#repframeworkoverview">Replication Manager Overview</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="apioverview.html#repapioverview">Replication Base API Overview</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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There are two ways that you can choose to implement
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replication in your transactional application. The first,
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and preferred, mechanism is to use the pre-packaged
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Replication Manager that comes with the
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DB distribution. This framework should be sufficient
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for most customers.
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</p>
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<p>
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If for some reason the Replication Manager
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does not meet your application's technical requirements,
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you will have to use the Replication Base APIs available
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through the Berkeley DB library to write your own custom
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replication framework.
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</p>
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<p>
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Both of these approaches are described in slightly greater
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detail in this section. The bulk of the chapters later in
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this book are dedicated to these two replication
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implementation mechanisms.
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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="repframeworkoverview"></a>Replication Manager Overview</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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DB's pre-packaged Replication Manager exists
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as a layer on top of the DB library. The Replication Manager is a
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multi-threaded implementation that allows you to easily add
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replication to your existing transactional application.
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<span>
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You access and manage the Replication Manager using methods that are
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available off the
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<code class="classname">DbEnv</code>
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class.
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</span>
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</p>
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<p>
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The Replication Manager:
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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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Provides a multi-threaded communications layer
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using pthreads (on Unix-style systems and
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similar derivatives such as Mac OS X), or
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Windows threads on Microsoft Windows systems.
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</p>
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</li>
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<li>
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<p>
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Uses TCP/IP sockets. Network traffic is
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handled via threads that handle inbound and
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outbound messages. However, each
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process uses a single socket
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that is shared using <code class="function">select()</code>.
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</p>
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<p>
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Note that for this reason, the Replication Manager is
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limited to a maximum of 60 replicas (on
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Windows) and approximately 1000 replicas (on
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Unix and related systems), depending on how
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your system is configured.
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</p>
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</li>
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<li>
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<p>
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Requires that only one instance of the
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environment handle 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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Upon application startup, a master can be
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selected either manually or via elections.
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After startup time, however, during the course of
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normal operations it is possible for the
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replication group to need to locate a new master (due
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to network or other hardware related problems,
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for example) and in this scenario elections are
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always used to select the new master.
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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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If your application has technical requirements that do
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not conform to the implementation provided by the
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Replication Manager, you must write implement replication
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using the DB Replication Base APIs. See
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the next section for introductory details.
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</p>
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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="repapioverview"></a>Replication Base API Overview</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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The Replication Base API is a series of Berkeley DB library
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classes and methods that you can use to build your own
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replication infrastructure. You should use the
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Base API only if the Replication Manager does not meet your
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application's technical requirements.
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</p>
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<p>
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To make use of the Base API, you must write your
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own networking code. This frees you from the technical
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constraints imposed by the Replication Manager. For example, by
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writing your own framework, you can:
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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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Use a threading package other than
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pthreads (Unix) or Windows threads
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(Microsoft Windows). This might be interesting
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to you if you are using a platform
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whose preferred threading package
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is something other than (for
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example) pthreads, such as is the case for
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Sun Microsystem's Solaris operating systems.
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</p>
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</li>
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<li>
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<p>
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Implement your own sockets. The
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Replication Manager uses TCP/IP sockets. While
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this should be acceptable for the
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majority of applications, sometimes
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UDP or even raw sockets might be
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desired.
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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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For information on writing a replicated application
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using the Berkeley DB Replication Base APIs, see the
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<em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
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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>
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<td width="40%" align="left"><a accesskey="p" href="repadvantage.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="elections.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">Replication Benefits </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"> Holding Elections</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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