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<!--$Id: mutex_stat.so,v 10.4 2007/09/21 20:06:03 bostic Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB: DbEnv::mutex_stat</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_stat</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_stat(DB_MUTEX_STAT **statp, u_int32_t flags); <p> int DbEnv::mutex_stat_print(u_int32_t flags); </pre></b> <hr size=1 noshade> <b>Description: DbEnv::mutex_stat</b> <p>The DbEnv::mutex_stat method returns the mutex subsystem statistics.</p> <p>The DbEnv::mutex_stat method creates a statistical structure of type DB_MUTEX_STAT and copies a pointer to it into a user-specified memory location.</p> <p>Statistical structures are stored in allocated memory. If application-specific allocation routines have been declared (see <a href="../../db4-devel-4.7.25/api_cxx/env_set_alloc.html">DbEnv::set_alloc</a> for more information), they are used to allocate the memory; otherwise, the standard C library <b>malloc</b>(3) is used. The caller is responsible for deallocating the memory. To deallocate the memory, free the memory reference; references inside the returned memory need not be individually freed.</p> <p>The following DB_MUTEX_STAT fields will be filled in:</p> <br> <b>u_int32_t st_mutex_align;</b><ul compact><li>The mutex alignment, in bytes.</ul> <b>u_int32_t st_mutex_tas_spins;</b><ul compact><li>The number of times test-and-set mutexes will spin without blocking.</ul> <b>int st_mutex_cnt;</b><ul compact><li>The total number of mutexes configured.</ul> <b>u_int32_t st_mutex_free;</b><ul compact><li>The number of mutexes currently available.</ul> <b>u_int32_t st_mutex_inuse;</b><ul compact><li>The number of mutexes currently in use.</ul> <b>u_int32_t st_mutex_inuse_max;</b><ul compact><li>The maximum number of mutexes ever in use.</ul> <b>roff_t st_regsize;</b><ul compact><li>The size of the mutex region, in bytes.</ul> <b>u_int32_t st_region_wait;</b><ul compact><li>The number of times that a thread of control was forced to wait before obtaining the mutex region mutex.</ul> <b>u_int32_t st_region_nowait;</b><ul compact><li>The number of times that a thread of control was able to obtain the mutex region mutex without waiting.</ul> <br> <p>The DbEnv::mutex_stat method may not be called before the <a href="../../db4-devel-4.7.25/api_cxx/env_open.html">DbEnv::open</a> method is called.</p> <p>The DbEnv::mutex_stat 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>flags</b><ul compact><li>The <b>flags</b> parameter must be set to 0 or the following value: <br> <b><a name="DB_STAT_CLEAR">DB_STAT_CLEAR</a></b><ul compact><li>Reset statistics after returning their values.</ul> <br></ul> <b>statp</b><ul compact><li>The <b>statp</b> parameter references memory into which a pointer to the allocated statistics structure is copied.</ul> <br> <br><b>Errors</b> <p>The DbEnv::mutex_stat 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_stat_print</b> <p>The DbEnv::mutex_stat_print method displays the mutex subsystem statistical information, as described for the DbEnv::mutex_stat method. The information is printed to a specified output channel (see the <a href="../../db4-devel-4.7.25/api_cxx/env_set_msgfile.html">DbEnv::set_msgfile</a> method for more information), or passed to an application callback function (see the <a href="../../db4-devel-4.7.25/api_cxx/env_set_msgcall.html">DbEnv::set_msgcall</a> method for more information).</p> <p>The DbEnv::mutex_stat_print method may not be called before the <a href="../../db4-devel-4.7.25/api_cxx/env_open.html">DbEnv::open</a> method is called.</p> <p>The DbEnv::mutex_stat_print 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>flags</b><ul compact><li>The <b>flags</b> parameter must be set to 0 or by bitwise inclusively <b>OR</b>'ing together one or more of the following values: <br> <b><a name="DB_STAT_ALL">DB_STAT_ALL</a></b><ul compact><li>Display all available information.</ul> <b><a name="DB_STAT_CLEAR">DB_STAT_CLEAR</a></b><ul compact><li>Reset statistics after displaying their values.</ul> <br></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. 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