<!--$Id: mutex_stat.so,v 10.3 2007/06/22 16:57:16 bostic Exp $--> <!--Copyright (c) 1997,2007 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> <h3>DbEnv::mutex_stat</h3> </td> <td align=right> <a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a> <a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td> </tr></table> <hr size=1 noshade> <tt> <h3><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></h3> <hr size=1 noshade> <h3>Description: DbEnv::mutex_stat</h3> <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="../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> <dl compact> <dt>u_int32_t st_mutex_align;<dd>The mutex alignment, in bytes. <dt>u_int32_t st_mutex_tas_spins;<dd>The number of times test-and-set mutexes will spin without blocking. <dt>int st_mutex_cnt;<dd>The total number of mutexes configured. <dt>u_int32_t st_mutex_free;<dd>The number of mutexes currently available. <dt>u_int32_t st_mutex_inuse;<dd>The number of mutexes currently in use. <dt>u_int32_t st_mutex_inuse_max;<dd>The maximum number of mutexes ever in use. <dt>roff_t st_regsize;<dd>The size of the mutex region, in bytes. <dt>u_int32_t st_region_wait;<dd>The number of times that a thread of control was forced to wait before obtaining the mutex region mutex. <dt>u_int32_t st_region_nowait;<dd>The number of times that a thread of control was able to obtain the mutex region mutex without waiting. </dl> <p>The DbEnv::mutex_stat method may not be called before the <a href="../api_cxx/env_open.html">DbEnv::open</a> method has been 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> <h3>Parameters</h3> <dl compact> <dt><b>flags</b><dd>The <b>flags</b> parameter must be set to 0 or the following value: <dl compact> <dt><a name="DB_STAT_CLEAR">DB_STAT_CLEAR</a><dd>Reset statistics after returning their values. </dl> <dt><b>statp</b><dd>The <b>statp</b> parameter references memory into which a pointer to the allocated statistics structure is copied. </dl> <h3>Errors</h3> <p>The DbEnv::mutex_stat 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> <dl compact> <dt>EINVAL<dd>An invalid flag value or parameter was specified. </dl> <hr size=1 noshade> <h3>Description: DbEnv::mutex_stat_print</h3> <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="../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="../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="../api_cxx/env_open.html">DbEnv::open</a> method has been 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> <h3>Parameters</h3> <dl compact> <dt><b>flags</b><dd>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: <dl compact> <dt><a name="DB_STAT_ALL">DB_STAT_ALL</a><dd>Display all available information. <dt><a name="DB_STAT_CLEAR">DB_STAT_CLEAR</a><dd>Reset statistics after displaying their values. </dl> </dl> <hr size=1 noshade> <h3>Class</h3> <a href="../api_cxx/env_class.html">DbEnv</a> <h3>See Also</h3> <a href="../api_cxx/env_list.html">Database Environments and Related Methods</a> </tt> <table width="100%"><tr><td><br></td><td align=right> <a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a> </td></tr></table> <p><font size=1>Copyright (c) 1996,2007 Oracle. 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