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<!--$Id: mutex_set_tas_spins.so,v 10.30 2005/07/20 16:34:01 bostic Exp $-->
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<title>Berkeley DB: DB_ENV->mutex_set_tas_spins</title>
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<h3>DB_ENV->mutex_set_tas_spins</h3>
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<h3><pre>
#include <db.h>
<p>
int
DB_ENV->mutex_set_tas_spins(DB_ENV *dbenv, u_int32_t tas_spins);
<p>
int
DB_ENV->mutex_get_tas_spins(DB_ENV *dbenv, u_int32_t *tas_spinsp);
</pre></h3>
<hr size=1 noshade>
<h3>Description: DB_ENV->mutex_set_tas_spins</h3>
<p>Specify that test-and-set mutexes should spin <b>tas_spins</b> times
without blocking. The value defaults to 1 on uniprocessor systems and
to 50 times the number of processors on multiprocessor systems.</p>
<p>The database environment's test-and-set spin count may also be configured using the
environment's <b>DB_CONFIG</b> file. The syntax of the entry in that
file is a single line with the string "set_tas_spins", one or more whitespace
characters, and the number of spins.
Because the <b>DB_CONFIG</b> 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_tas_spins method configures operations performed using the specified
<a href="../api_c/env_class.html">DB_ENV</a> handle, not all operations performed on the underlying
database environment.</p>
<p>The DB_ENV->mutex_set_tas_spins method may be called at any time during the life of the
application.</p>
<p>The DB_ENV->mutex_set_tas_spins method
returns a non-zero error value on failure
and 0 on success.
</p>
<h3>Parameters</h3>
<dl compact>
<dt><b>tas_spins</b><dd>The <b>tas_spins</b> parameter is the number of spins test-and-set
mutexes should execute before blocking.
</dl>
<h3>Errors</h3>
<p>The DB_ENV->mutex_set_tas_spins method
may fail and return one of the following non-zero errors:</p>
<dl compact>
<dt>EINVAL<dd>An
invalid flag value or parameter was specified.
</dl>
<hr size=1 noshade>
<h3>Description: DB_ENV->mutex_get_tas_spins</h3>
<p>The DB_ENV->mutex_get_tas_spins method returns the test-and-set spin count.</p>
<p>The DB_ENV->mutex_get_tas_spins method may be called at any time during the life of the
application.</p>
<p>The DB_ENV->mutex_get_tas_spins method
returns a non-zero error value on failure
and 0 on success.
</p>
<h3>Parameters</h3>
<dl compact>
<dt><b>tas_spinsp</b><dd>The DB_ENV->mutex_get_tas_spins method returns the
test-and-set spin count in <b>tas_spinsp</b>.
</dl>
<hr size=1 noshade>
<h3>Class</h3>
<a href="../api_c/env_class.html">DB_ENV</a>
<h3>See Also</h3>
<a href="../api_c/env_list.html">Database Environments and Related Methods</a>
</tt>
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