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<!--$Id: mutex_set_align.so,v 10.1 2005/07/20 16:34:00 bostic Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB: DbEnv::mutex_set_align</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> </head> <body bgcolor=white> <table width="100%"><tr valign=top> <td> <b>DbEnv::mutex_set_align</b> </td> <td align=right> <a href="../../db4-devel-4.7.25/api_cxx/api_core.html"><img src="../../db4-devel-4.7.25/images/api.gif" alt="API"></a> <a href="../../db4-devel-4.7.25/ref/toc.html"><img src="../../db4-devel-4.7.25/images/ref.gif" alt="Ref"></a></td> </tr></table> <hr size=1 noshade> <tt> <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> <hr size=1 noshade> <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="../../db4-devel-4.7.25/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="../../db4-devel-4.7.25/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="../../db4-devel-4.7.25/api_cxx/env_class.html">DbEnv</a> handle.</p> <p>The DbEnv::mutex_set_align method may not be called after the <a href="../../db4-devel-4.7.25/api_cxx/env_open.html">DbEnv::open</a> method is called. If the database environment already exists when <a href="../../db4-devel-4.7.25/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="../../db4-devel-4.7.25/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> <hr size=1 noshade> <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> <hr size=1 noshade> <br><b>Class</b> <a href="../../db4-devel-4.7.25/api_cxx/env_class.html">DbEnv</a> <br><b>See Also</b> <a href="../../db4-devel-4.7.25/api_cxx/env_list.html">Database Environments and Related Methods</a> </tt> <table width="100%"><tr><td><br></td><td align=right> <a href="../../db4-devel-4.7.25/api_cxx/api_core.html"><img src="../../db4-devel-4.7.25/images/api.gif" alt="API"></a><a href="../../db4-devel-4.7.25/ref/toc.html"><img src="../../db4-devel-4.7.25/images/ref.gif" alt="Ref"></a> </td></tr></table> <p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> </body> </html>
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