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<b>DbEnv::mutex_set_align</b>
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<b><pre>
#include <db_cxx.h>
<p>
int
DbEnv::mutex_set_align(u_int32_t align);
<p>
int
DbEnv::mutex_get_align(u_int32_t *alignp);
</pre></b>
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<b>Description: DbEnv::mutex_set_align</b>
<p>Set the mutex alignment, in bytes.</p>
<p>It is sometimes advantageous to align mutexes on specific byte
boundaries in order to minimize cache line collisions. The
DbEnv::mutex_set_align method specifies an alignment for mutexes allocated
by Berkeley DB.</p>
<p>The database environment's mutex alignment may also be configured using the
environment's <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file. The syntax of the entry in that
file is a single line with the string "mutex_set_align", one or more whitespace
characters, and the mutex alignment in bytes.
Because the <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file is read when the database environment
is opened, it will silently overrule configuration done before that
time.</p>
<p>The DbEnv::mutex_set_align method configures a database environment, not only operations
performed using the specified <a href="../api_cxx/env_class.html">DbEnv</a> handle.</p>
<p>The DbEnv::mutex_set_align method may not be called after the <a href="../api_cxx/env_open.html">DbEnv::open</a> method is
called.
If the database environment already exists when
<a href="../api_cxx/env_open.html">DbEnv::open</a> is called, the information specified to DbEnv::mutex_set_align
will be ignored.
</p>
<p>The DbEnv::mutex_set_align 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.
</p>
<b>Parameters</b> <br>
<b>align</b><ul compact><li>The <b>align</b> parameter is the mutex alignment, in bytes. The mutex
alignment must be a power-of-two.</ul>
<br>
<br><b>Errors</b>
<p>The DbEnv::mutex_set_align method
may fail and throw
<a href="../api_cxx/except_class.html">DbException</a>,
encapsulating one of the following non-zero errors, or return one of
the following non-zero errors:</p>
<br>
<b>EINVAL</b><ul compact><li>An
invalid flag value or parameter was specified.</ul>
<br>
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<b>Description: DbEnv::mutex_get_align</b>
<p>The DbEnv::mutex_get_align method returns the mutex alignment, in bytes.</p>
<p>The DbEnv::mutex_get_align method may be called at any time during the life of the
application.</p>
<p>The DbEnv::mutex_get_align 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.
</p>
<b>Parameters</b> <br>
<b>alignp</b><ul compact><li>The DbEnv::mutex_get_align method returns the
mutex alignment, in bytes in <b>alignp</b>.</ul>
<br>
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<br><b>Class</b>
<a href="../api_cxx/env_class.html">DbEnv</a>
<br><b>See Also</b>
<a href="../api_cxx/env_list.html">Database Environments and Related Methods</a>
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