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213 lines
8.5 KiB
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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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>DB_ENV->rep_set_request()</title>
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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 C API Reference" />
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<link rel="up" href="rep.html" title="Chapter 10. Replication Methods" />
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<link rel="prev" href="reppriority.html" title="DB_ENV->rep_set_priority()" />
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<p>Library Version 11.2.5.3</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">DB_ENV->rep_set_request()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="reppriority.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 10.
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Replication Methods
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="repset_timeout.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="repset_request"></a>DB_ENV->rep_set_request()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db.h>
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int
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DB_ENV->rep_set_request(DB_ENV *env, u_int32_t min, u_int32_t max); </pre>
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<p>
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The <code class="methodname">DB_ENV->rep_set_request()</code> method sets a
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threshold for the minimum and maximum time that a client waits
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before requesting retransmission of a missing message.
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Specifically, if the client detects a gap in the sequence of
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incoming log records or database pages, Berkeley DB will wait for
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at least <span class="bold"><strong>min</strong></span> microseconds before
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requesting retransmission of the missing record. Berkeley DB will
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double that amount before requesting the same missing record
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again, and so on, up to a maximum threshold of
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<span class="bold"><strong>max</strong></span> microseconds.
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</p>
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<p>
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These values are thresholds only. Replication Manager applications
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use these values to determine when to automatically request
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retransmission of missing messages. For Base API applications,
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Berkeley DB has no thread available in the library as a timer, so
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the threshold is only checked when a thread enters the Berkeley DB
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library to process an incoming replication message. Any amount of
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time may have passed since the last message arrived and Berkeley
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DB only checks whether the amount of time since a request was made
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is beyond the threshold value or not.
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</p>
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<p>
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By default the minimum is 40000 and the maximum is 1280000 (1.28
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seconds). These defaults are fairly arbitrary and the application
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likely needs to adjust these. The values should be based on
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expected load and performance characteristics of the master and
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client host platforms and transport infrastructure as well as
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round-trip message time.
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</p>
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<p>
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The database environment's replication subsystem may also be
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configured using the environment's <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file. The syntax
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of the entry in that file is a single line with the string
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"rep_set_request", one or more whitespace characters, and the
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request times specified in two parts: the min and the max. For
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example, "rep_set_request 40000 1280000". Because the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a>
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file is read when the database environment is opened, it will
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silently overrule configuration done before that time.
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</p>
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<p>
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The <code class="methodname">DB_ENV->rep_set_request()</code> method
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configures a database environment, not only operations performed
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using the specified <a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
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handle.
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</p>
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<p>
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The <code class="methodname">DB_ENV->rep_set_request()</code> method may be
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called at any time during the life of the application.
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</p>
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<p>
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The <code class="methodname">DB_ENV->rep_set_request()</code> <span>
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<span>
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method returns a non-zero error value on failure and 0 on success.
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</span>
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</span>
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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="idp62139880"></a>Parameters</h3>
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</div>
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</div>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="idp62139680"></a>min</h4>
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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 minimum number of microseconds a client waits before requesting
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retransmission.
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</p>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="idp62150904"></a>max</h4>
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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 maximum number of microseconds a client waits before requesting
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retransmission.
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</p>
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</div>
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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="idp62140960"></a>Errors</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 <code class="methodname">DB_ENV->rep_set_request()</code> <span>
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<span>
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method may fail and return one of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" 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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<h4 class="title"><a id="idp62131992"></a>EINVAL</h4>
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</div>
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</div>
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</div>
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<p>
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An invalid flag value or parameter was specified.
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</p>
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</div>
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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="idp62130472"></a>Class</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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<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
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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="idp62141624"></a>See Also</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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<a class="xref" href="rep.html#replist" title="Replication and Related Methods">Replication and Related Methods</a>
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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="reppriority.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="repset_timeout.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">DB_ENV->rep_set_priority() </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"> DB_ENV->rep_set_timeout()</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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