2011-09-13 17:44:24 +00:00
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<title>DB_ENV->mutex_set_align()</title>
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<link rel="up" href="mutex.html" title="Chapter 9. Mutex Methods" />
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<p>Library Version 11.2.5.2</p>
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<table width="100%" summary="Navigation header">
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<th colspan="3" align="center">DB_ENV->mutex_set_align()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="mutexlock.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 9.
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Mutex Methods
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="mutexset_increment.html">Next</a></td>
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<div>
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<h2 class="title" style="clear: both"><a id="mutexset_align"></a>DB_ENV->mutex_set_align()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db.h>
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int
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DB_ENV->mutex_set_align(DB_ENV *dbenv, u_int32_t align); </pre>
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<p>
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Set the mutex alignment, in bytes.
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</p>
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<p>
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It is sometimes advantageous to align mutexes on specific byte
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boundaries in order to minimize cache line collisions. The
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<code class="methodname">DB_ENV->mutex_set_align()</code> method specifies an alignment for mutexes
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allocated by Berkeley DB.
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</p>
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<p>
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The database environment's mutex alignment may also be configured
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using the environment's <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file. The
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syntax of the entry in that file is a single line with the string
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"mutex_set_align", one or more whitespace characters, and the mutex
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alignment in bytes. Because the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file is
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read when the database environment is opened, it will silently
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overrule configuration done before that time.
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</p>
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<p>
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The <code class="methodname">DB_ENV->mutex_set_align()</code> method configures a database
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environment, not only operations performed using the specified
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<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> handle.
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</p>
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<p>
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The <code class="methodname">DB_ENV->mutex_set_align()</code> method may not be called after the
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<a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> method is
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called. If the database environment already exists when
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<a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> is called, the
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information specified to <code class="methodname">DB_ENV->mutex_set_align()</code> will be ignored.
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</p>
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<p>
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The <code class="methodname">DB_ENV->mutex_set_align()</code> <span>
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<span>
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method returns a non-zero error value on failure and 0 on success.
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</span>
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</span>
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</p>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h3 class="title"><a id="id3742008"></a>Parameters</h3>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h4 class="title"><a id="id3742108"></a>align</h4>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>align</strong></span> parameter is the mutex
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alignment, in bytes. The mutex alignment must be a power-of-two.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h3 class="title"><a id="id3741731"></a>Errors</h3>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<p>
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The <code class="methodname">DB_ENV->mutex_set_align()</code> <span>
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<span>
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method may fail and return one of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h4 class="title"><a id="id3742401"></a>EINVAL</h4>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<p>
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If the method was called after <a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a>
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was called; or if an invalid flag value or parameter was specified.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h3 class="title"><a id="id3742383"></a>Class</h3>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<p>
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<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
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</p>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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2011-12-20 00:07:10 +00:00
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<h3 class="title"><a id="id3741887"></a>See Also</h3>
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2011-09-13 17:44:24 +00:00
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</div>
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</div>
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</div>
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<p>
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<a class="xref" href="mutex.html#mutexlist" title="Mutex Methods">Mutex Methods</a>
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</p>
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<td width="40%" align="left" valign="top">DB_ENV->mutex_lock() </td>
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<td width="40%" align="right" valign="top"> DB_ENV->mutex_set_increment()</td>
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