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<h2 class="title" style="clear: both"><a id="mutexset_increment"></a>DB_ENV->mutex_set_increment()</h2>
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<pre class="programlisting">#include <db.h>
int
DB_ENV->mutex_set_increment(DB_ENV *dbenv, u_int32_t increment); </pre>
<p>
Configure the number of additional mutexes to allocate.
</p>
<p>
If an application will allocate mutexes for its own use,
the <code class="methodname">DB_ENV->mutex_set_increment()</code> method is used to add a
number of mutexes to the default allocation.
</p>
<p>
Calling the <code class="methodname">DB_ENV->mutex_set_increment()</code> method discards any value
previously set using the <code class="methodname">DB_ENV->mutex_set_max()</code> method.
</p>
<p>
The database environment's number of additional mutexes 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
"mutex_set_increment", one or more whitespace characters, and the
number of additional mutexes. 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">DB_ENV->mutex_set_increment()</code> method configures a database
environment, not only operations performed using the specified
<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> handle.
</p>
<p>
The <code class="methodname">DB_ENV->mutex_set_increment()</code> method may not be called after the
<a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> method is
called. If the database environment already exists when
<a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> is called, the
information specified to <code class="methodname">DB_ENV->mutex_set_increment()</code> will be
ignored.
</p>
<p>
The <code class="methodname">DB_ENV->mutex_set_increment()</code> <span>
<span>
method returns a non-zero error value on failure and 0 on success.
</span>
</span>
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<h3 class="title"><a id="id1694422"></a>Parameters</h3>
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<h4 class="title"><a id="id1694436"></a>increment</h4>
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<p>
The <span class="bold"><strong>increment</strong></span> parameter is the number
of additional mutexes to allocate.
</p>
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<h3 class="title"><a id="id1694617"></a>Errors</h3>
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<p>
The <code class="methodname">DB_ENV->mutex_set_increment()</code> <span>
<span>
method may fail and 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="id1694469"></a>EINVAL</h4>
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<p>
If the method was called after <a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a>
was called; or if an invalid flag value or parameter was specified.
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<h3 class="title"><a id="id1694549"></a>Class</h3>
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<p>
<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
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<h3 class="title"><a id="id1694526"></a>See Also</h3>
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<a class="xref" href="mutex.html#mutexlist" title="Mutex Methods">Mutex Methods</a>
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