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<title>DbEnv::rep_set_clockskew()</title>
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<link rel="up" href="rep.html" title="Chapter 11. Replication Methods" />
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<tr>
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<th colspan="3" align="center">DbEnv::rep_set_clockskew()</th>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="repmessage.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 11.
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Replication Methods
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="repconfig.html">Next</a></td>
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</tr>
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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="repclockskew"></a>DbEnv::rep_set_clockskew()</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_cxx.h>
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int
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DbEnv::rep_set_clockskew(u_int32_t fast_clock, u_int32_t slow_clock); </pre>
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<p>
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The <code class="methodname">DbEnv::rep_set_clockskew()</code> method sets the
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clock skew ratio among replication group members based on the fastest
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and slowest measurements among the group for use with master leases.
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Calling this method is optional; the default values for clock skew
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assume no skew. The user must also configure leases via the
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<a class="xref" href="repconfig.html" title="DbEnv::rep_set_config()">DbEnv::rep_set_config()</a>
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method. Additionally, the user must also set the master lease timeout
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via the
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<a class="xref" href="repset_timeout.html" title="DbEnv::rep_set_timeout()">DbEnv::rep_set_timeout()</a>
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method. For Base API applications, the user must also set the number of
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sites in the replication group via the
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<a class="xref" href="repnsites.html" title="DbEnv::rep_set_nsites()">DbEnv::rep_set_nsites()</a>
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method. These methods may be called in any order. For a description
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of the clock skew values, see
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<a href="../../programmer_reference/rep_clock_skew.html" class="olink">Clock skew</a>
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in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>. For a description of
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master leases, see
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<a href="../../programmer_reference/rep_lease.html" class="olink">Master leases</a> in the
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<em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
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</p>
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<p>
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These arguments can be used to express either raw measurements of a
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clock timing experiment or a percentage across machines. For example, if
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a group of sites has a 2% variance, then <span class="bold"><strong>fast_clock</strong></span> should be set to 102, and
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<span class="bold"><strong>slow_clock</strong></span> should be set to 100. Or,
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for a 0.03% difference, you can use 10003 and 10000 respectively.
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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 of
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the entry in that file is a single line with the string
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"rep_set_clockskew", one or more whitespace characters, and the
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clockskew specified in two parts: the fast_clock and the
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slow_clock. For example, "rep_set_clockskew 102 100". Because the
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<a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file is read when the database environment is opened,
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it will 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">DbEnv::rep_set_clockskew()</code> method configures a database
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environment, not only operations performed using the specified
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<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle.
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</p>
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<p>
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The <code class="methodname">DbEnv::rep_set_clockskew()</code> method may not be called after the
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<a class="xref" href="repmgrstart.html" title="DbEnv::repmgr_start()">DbEnv::repmgr_start()</a> or
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<a class="xref" href="repstart.html" title="DbEnv::rep_start()">DbEnv::rep_start()</a>
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methods are called.
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</p>
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<p>
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The <code class="methodname">DbEnv::rep_set_clockskew()</code> <span>
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<span>
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method either returns a non-zero error value or throws an
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exception that encapsulates a non-zero error value on
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failure, and returns 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="id3639664"></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="id3639656"></a>fast_clock</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 value, relative to the <span class="bold"><strong>slow_clock</strong></span>,
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of the fastest clock in the group of sites.
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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="id3639460"></a>slow_clock</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 value of the slowest clock in the group of sites.
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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="id3639064"></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">DbEnv::rep_set_clockskew()</code> <span>
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<span>
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method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
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exception, encapsulating one of the following non-zero errors, or return one
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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="id3639872"></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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If the method was called after replication is started with a
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call to the
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<a class="xref" href="repmgrstart.html" title="DbEnv::repmgr_start()">DbEnv::repmgr_start()</a> or the
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<a class="xref" href="repstart.html" title="DbEnv::rep_start()">DbEnv::rep_start()</a> method; or if
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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="id3639169"></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 DbEnv Handle">DbEnv</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="id3639668"></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="repmessage.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="repconfig.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">DbEnv::rep_process_message() </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"> DbEnv::rep_set_config()</td>
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</body>
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</html>
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