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Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
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<p>Library Version 11.2.5.2</p>
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<th colspan="3" align="center">DbEnv::rep_set_request()</th>
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<tr>
<td width="20%" align="left"><a accesskey="p" href="reppriority.html">Prev</a> </td>
<th width="60%" align="center">Chapter 11. 
Replication Methods
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<div class="sect1" lang="en" xml:lang="en">
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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 &lt;db_cxx.h&gt;
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. Replication Manager applications
use these values to determine when to automatically request
retransmission of missing messages. For Base API applications,
Berkeley DB has no thread available in the library as a timer, so
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">
<div>
<div>
Release 5.2.36 on 9/14/2022
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<h3 class="title"><a id="id3641075"></a>Parameters</h3>
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</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
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<h4 class="title"><a id="id3641085"></a>min</h4>
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</div>
</div>
</div>
<p>
The minimum number of microseconds a client waits before requesting
retransmission.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
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<h4 class="title"><a id="id3641275"></a>max</h4>
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</div>
</div>
</div>
<p>
The maximum 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>
Release 5.2.36 on 9/14/2022
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<h3 class="title"><a id="id3641107"></a>Errors</h3>
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</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>
Release 5.2.36 on 9/14/2022
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<h4 class="title"><a id="id3641248"></a>EINVAL</h4>
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</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>
Release 5.2.36 on 9/14/2022
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<h3 class="title"><a id="id3641226"></a>Class</h3>
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</div>
</div>
</div>
<p>
<a class="link" href="env.html" title="Chapter 5.  The DbEnv Handle">DbEnv</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
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<h3 class="title"><a id="id3641043"></a>See Also</h3>
Release 5.2.28 on 6/10/2011
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</div>
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<p>
<a class="xref" href="rep.html#replist" title="Replication and Related Methods">Replication and Related Methods</a>
</p>
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