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<b>DB_ENV->mutex_set_align</b>
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<b><pre>
#include <db.h>
<p>
int
DB_ENV->mutex_set_align(DB_ENV *dbenv, u_int32_t align);
<p>
int
DB_ENV->mutex_get_align(DB_ENV *dbenv, u_int32_t *alignp);
</pre></b>
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<b>Description: DB_ENV->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
DB_ENV->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 DB_ENV->mutex_set_align method configures a database environment, not only operations
performed using the specified <a href="../api_c/env_class.html">DB_ENV</a> handle.</p>
<p>The DB_ENV->mutex_set_align method may not be called after the <a href="../api_c/env_open.html">DB_ENV->open</a> method is
called.
If the database environment already exists when
<a href="../api_c/env_open.html">DB_ENV->open</a> is called, the information specified to DB_ENV->mutex_set_align
will be ignored.
</p>
<p>The DB_ENV->mutex_set_align method
returns a non-zero error value on failure
and 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 DB_ENV->mutex_set_align method
may fail and 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: DB_ENV->mutex_get_align</b>
<p>The DB_ENV->mutex_get_align method returns the mutex alignment, in bytes.</p>
<p>The DB_ENV->mutex_get_align method may be called at any time during the life of the
application.</p>
<p>The DB_ENV->mutex_get_align method
returns a non-zero error value on failure
and 0 on success.
</p>
<b>Parameters</b> <br>
<b>alignp</b><ul compact><li>The DB_ENV->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_c/env_class.html">DB_ENV</a>
<br><b>See Also</b>
<a href="../api_c/env_list.html">Database Environments and Related Methods</a>
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<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font>
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