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<h2 class="title" style="clear: both"><a id="mutexset_max"></a>DbEnv::mutex_set_max()</h2>
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<pre class="programlisting">#include <db_cxx.h>
int
DbEnv::mutex_set_max(u_int32_t max); </pre>
<p>
Configure the total number of mutexes to allocate.
</p>
<p>
Berkeley DB allocates a default number of mutexes based on the initial
configuration of the database environment. That default calculation
may be too small if the application has an unusual need for mutexes
(for example, if the application opens an unexpectedly large number of
databases) or too large (if the application is trying to minimize its
memory footprint). The <code class="methodname">DbEnv::mutex_set_max()</code> method is used to
specify an absolute number of mutexes to allocate.
</p>
<p>
Calling the <code class="methodname">DbEnv::mutex_set_max()</code> method discards any value
previously set using the <code class="methodname">DbEnv::mutex_set_increment()</code> method.
</p>
<p>
The database environment's total number of 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_max", one or more whitespace characters, and the total
number of 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">DbEnv::mutex_set_max()</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::mutex_set_max()</code> method may not be called after the
<a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method is called.
If the database environment already exists when
<a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> is called, the
information specified to <code class="methodname">DbEnv::mutex_set_max()</code> will be ignored.
</p>
<p>
The <code class="methodname">DbEnv::mutex_set_max()</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>
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<div class="sect2" lang="en" xml:lang="en">
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<h3 class="title"><a id="idp53888104"></a>Parameters</h3>
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<div class="sect3" lang="en" xml:lang="en">
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<div>
<h4 class="title"><a id="idp53888488"></a>max</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>max</strong></span> parameter is the absolute
number of mutexes to allocate.
</p>
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<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
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<h3 class="title"><a id="idp53868072"></a>Errors</h3>
</div>
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<p>
The <code class="methodname">DbEnv::mutex_set_max()</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>
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<h4 class="title"><a id="idp53898048"></a>EINVAL</h4>
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An invalid flag value or parameter was specified.
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<h3 class="title"><a id="idp53896752"></a>Class</h3>
</div>
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<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
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<h3 class="title"><a id="idp53892064"></a>See Also</h3>
</div>
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<p>
<a class="xref" href="mutex.html#mutexlist" title="Mutex Methods">Mutex Methods</a>
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