mirror of
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Yasuhiro KIMURA
212 lines
8.8 KiB
HTML
212 lines
8.8 KiB
HTML
<?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>Ex_rep_chan: a Replication Manager channel example</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="Berkeley DB Programmer's Reference Guide" />
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<link rel="up" href="rep.html" title="Chapter 12. Berkeley DB Replication" />
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<link rel="prev" href="rep_ex_rq.html" title="Ex_rep_base: putting it all together" />
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<link rel="next" href="bdb_slices.html" title="Chapter 13. Berkeley DB Slice Support" />
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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 18.1.40</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">Ex_rep_chan: a Replication Manager channel example</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="rep_ex_rq.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 12. Berkeley DB Replication </th>
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<td width="20%" align="right"> <a accesskey="n" href="bdb_slices.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="rep_ex_chan"></a>Ex_rep_chan: a Replication Manager channel example</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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Ex_rep_chan, found in the
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<code class="filename">examples/c/ex_rep_chan</code> subdirectory
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of the Berkeley DB distribution, is a simple but complete
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demonstration of a replicated application that uses the
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Replication Manager feature of channels to perform write
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forwarding. The application is a mock stock ticker. Although
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similar to the ex_rep_mgr example program, this example
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differs in that it provides an example of using Replication
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Manager message channels. Any site accepts a command to write
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data to the database. If the site is a client, then, using the
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channels feature, the application forwards the request to the
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master site. If the site is a master then the request is
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automatically handled locally. You can read and write stock
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values at any site without needing to know what site is
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currently the master.
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</p>
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<p>
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The set of supported commands can be viewed with either the
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<span class="bold"><strong>help</strong></span> or the <span class="bold"><strong>?</strong></span> command. Several commands work
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with key/data pairs where the key is a stock symbol and the
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data is its value.
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</p>
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<p>
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The command to retrieve and print the current site's
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database contents is <span class="bold"><strong>print</strong></span> or
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simply an empty input line. To read the contents of the
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master's database from any site use the <span class="bold"><strong>get key key ...</strong></span>
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command. That command will
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forward the read request to the master if necessary and return
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the key/data pairs for all given keys.
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</p>
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<p>
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There are two commands to put data into the database. Both
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commands take one or more key/data pairs, all of which are
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written into the database in a single transaction at the
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master site. The <span class="bold"><strong>put</strong></span> command
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sends the data to the master site, and simply waits for a
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status response. The <span class="bold"><strong>put_sync</strong></span>
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command sends the data to the master site, and uses a
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transaction token returned by the master to wait for the
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contents of that put to be available on the local site. This
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serves as a demonstration of the <a class="link" href="rep_ryw.html" title="Read your writes consistency">read
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your writes</a> consistency feature.
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</p>
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<p>
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The Makefile created by the standard UNIX configuration
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will build the ex_rep_chan example on most platforms. Enter
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"make ex_rep_chan" to build it.
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</p>
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<p>
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The synopsis for the program is as follows:
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</p>
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<p>
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<code class="literal">ex_rep_chan <span class="bold"><strong>-h home</strong></span>
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<span class="bold"><strong>-l host:port</strong></span> [<span class="bold"><strong>-MC</strong></span>] [<span class="bold"><strong>-r
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host:port</strong></span>] [<span class="bold"><strong>-R
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host:port</strong></span>] [<span class="bold"><strong>-p
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priority</strong></span>] [<span class="bold"><strong>-v</strong></span>]</code>
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</p>
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<p>
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The options are as follows:
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</p>
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<div class="variablelist">
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<dl>
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<dt>
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<span class="term">
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<span class="bold"><strong>-h</strong></span>
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</span>
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</dt>
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<dd>
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Specify a home directory for the database
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environment.
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</dd>
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<dt>
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<span class="term">
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<span class="bold"><strong>-l</strong></span>
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</span>
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</dt>
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<dd>
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Listen on local host "host" at port "port" for
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incoming connections.
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</dd>
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<dt>
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<span class="term">
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<span class="bold"><strong>-M</strong></span>
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</span>
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</dt>
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<dd>
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Configure this process as a master.
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</dd>
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<dt>
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<span class="term">
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<span class="bold"><strong>-C</strong></span>
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</span>
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</dt>
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<dd>
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Configure this process as a client.
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</dd>
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<dt>
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<span class="term">
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<span class="bold"><strong>-r</strong></span>
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</span>
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</dt>
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<dd>
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Identifies the helper site used for joining the
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group.
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</dd>
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<dt>
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<span class="term">
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<span class="bold"><strong>-R</strong></span>
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</span>
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</dt>
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<dd>
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Identifies a remote peer to be used for joining
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the group. This peer is used for syncing purposes. See
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<a class="xref" href="rep_mastersync.html#rep_c2c_sync" title="Client-to-client synchronization">Client-to-client synchronization</a> for more
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information.
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</dd>
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<dt>
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<span class="term">
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<span class="bold"><strong>-p</strong></span>
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</span>
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</dt>
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<dd>
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Set the election priority. See <a class="xref" href="rep_elect.html" title="Elections">Elections</a>
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for more information.
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</dd>
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<dt>
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<span class="term">
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<span class="bold"><strong>-v</strong></span>
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</span>
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</dt>
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<dd>
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Indicates that additional informational and
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debugging output should be enabled.
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</dd>
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</dl>
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</div>
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<p>
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A typical ex_rep_chan session begins with a command such as
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the following, to start a master:
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</p>
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<pre class="programlisting">ex_rep_chan -M -h DIR1 -l localhost:30100</pre>
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<p>
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and several clients:
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</p>
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<pre class="programlisting">ex_rep_chan -C -h DIR2 -l localhost:30101 -r localhost:30100
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ex_rep_chan -C -h DIR3 -l localhost:30102 -r localhost:30100
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ex_rep_chan -C -h DIR4 -l localhost:30103 -r localhost:30100</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="rep_ex_rq.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="rep.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="bdb_slices.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">Ex_rep_base: putting it all
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together </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"> Chapter 13. Berkeley DB Slice Support</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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