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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. This method is
deprecated. The maximum size of the mutex region is now inferred by
the sizes of the other memory structures, and so this method is no
longer needed. For example, the cache requires one mutex per page
in the cache. When you specify the cache size, DB assumes a
page size of 4K and allocates mutexes accordingly. If your page
size is different than 4K, you indicate this using
<a class="xref" href="envset_mp_pagesize.html" title="DbEnv::set_mp_pagesize()">DbEnv::set_mp_pagesize()</a>.
DB will then allocate the proper number of mutexes based on this new page size.
</p>
<p>
You can use this method to override DB's mutex calculation, but
it is not recommended to do so.
</p>
<p>
Calling the <code class="methodname">DbEnv::mutex_set_max()</code> method discards any value
previously set using the
<a class="xref" href="mutexset_increment.html" title="DbEnv::mutex_set_increment()">DbEnv::mutex_set_increment()</a> 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="idp9242024"></a>Parameters</h3>
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<div class="sect3" lang="en" xml:lang="en">
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<h4 class="title"><a id="idp9241376"></a>max</h4>
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</div>
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<p>
The <span class="bold"><strong>max</strong></span> parameter is the absolute
number of mutexes to allocate.
</p>
</div>
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<div class="sect2" lang="en" xml:lang="en">
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<h3 class="title"><a id="idp9233408"></a>Errors</h3>
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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>
</p>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp9252448"></a>EINVAL</h4>
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<p>
An invalid flag value or parameter was specified.
</p>
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<div class="sect2" lang="en" xml:lang="en">
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<h3 class="title"><a id="idp9251152"></a>Class</h3>
</div>
</div>
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<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="idp9246400"></a>See Also</h3>
</div>
</div>
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<p>
<a class="xref" href="mutex.html#mutexlist" title="Mutex Methods">Mutex Methods</a>
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