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<h2 class="title" style="clear: both"><a id="repset_request"></a>DbEnv::rep_set_request()</h2>
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<pre class="programlisting">#include <db_cxx.h>
int
DbEnv::rep_set_request(u_int32_t min, u_int32_t max); </pre>
<p>
The <code class="methodname">DbEnv::rep_set_request()</code> method sets a threshold for the
minimum and maximum time that a client waits before requesting retransmission of a missing
message. Specifically, if the client detects a gap in the sequence of incoming log records
or database pages, Berkeley DB will wait for at least <span class="bold"><strong>min</strong></span>
microseconds before requesting retransmission of the missing record. Berkeley DB will
double that amount before requesting the same missing record again, and so on, up to a
maximum threshold of <span class="bold"><strong>max</strong></span> microseconds.
</p>
<p>
These values are thresholds only. Since Berkeley DB has no thread
available in the library as a timer, the threshold is only checked
when a thread enters the Berkeley DB library to process an incoming
replication message. Any amount of time may have passed since the last
message arrived and Berkeley DB only checks whether the amount of time
since a request was made is beyond the threshold value or not.
</p>
<p>
By default the minimum is 40000 and the maximum is 1280000 (1.28
seconds). These defaults are fairly arbitrary and the application
likely needs to adjust these. The values should be based on expected
load and performance characteristics of the master and client host
platforms and transport infrastructure as well as round-trip message
time.
</p>
<p>
The database environment's replication subsystem may also be 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 the entry in that file is a single line with the string "rep_set_request", one or
more whitespace characters, and the request times specified in two parts: the min and the
max. For 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> file is read when the
database environment is opened, it will silently overrule configuration done before that
time.
</p>
<p>
The <code class="methodname">DbEnv::rep_set_request()</code> method configures a database
environment, not only operations performed using the specified
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle.
</p>
<p>
The <code class="methodname">DbEnv::rep_set_request()</code> method may be called at any time during
the life of the application.
</p>
<p>
The <code class="methodname">DbEnv::rep_set_request()</code> <span>
<span>
method either returns a non-zero error value or throws an
exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
</span>
</span>
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
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<h3 class="title"><a id="id1703775"></a>Parameters</h3>
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<div class="sect3" lang="en" xml:lang="en">
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<div>
<div>
<h4 class="title"><a id="id1704071"></a>max</h4>
</div>
</div>
</div>
<p>
The maximum number of microseconds a client waits before requesting
retransmission.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id1704142"></a>min</h4>
</div>
</div>
</div>
<p>
The minimum number of microseconds a client waits before requesting
retransmission.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id1704143"></a>Errors</h3>
</div>
</div>
</div>
<p>
The <code class="methodname">DbEnv::rep_set_request()</code> <span>
<span>
method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
exception, encapsulating one of the following non-zero errors, or return one
of the following non-zero errors:
</span>
</span>
</p>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id1704138"></a>EINVAL</h4>
</div>
</div>
</div>
<p>
An invalid flag value or parameter was specified.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id1704054"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
</p>
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<div class="sect2" lang="en" xml:lang="en">
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<h3 class="title"><a id="id1703778"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a class="xref" href="rep.html#replist" title="Replication and Related Methods">Replication and Related Methods</a>
</p>
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