Berkeley DB: DbEnv::mutex_stat
Description: Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++

### DbEnv::mutex_stat |

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###

    #include <db_cxx.h>

    int
    DbEnv::mutex_stat(DB_MUTEX_STAT **statp, u_int32_t flags);

    int
    DbEnv::mutex_stat_print(u_int32_t flags);

### Description: DbEnv::mutex_stat

The DbEnv::mutex_stat method returns the mutex subsystem statistics.

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.

Statistical structures are stored in allocated memory. If application-specific allocation routines have been declared (see DbEnv::set_alloc for more information), they are used to allocate the memory; otherwise, the standard C library malloc(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.

The following DB_MUTEX_STAT fields will be filled in:

u_int32_t st_mutex_align;
  The mutex alignment, in bytes.
u_int32_t st_mutex_tas_spins;
  The number of times test-and-set mutexes will spin without blocking.
int st_mutex_cnt;
  The total number of mutexes configured.
u_int32_t st_mutex_free;
  The number of mutexes currently available.
u_int32_t st_mutex_inuse;
  The number of mutexes currently in use.
u_int32_t st_mutex_inuse_max;
  The maximum number of mutexes ever in use.
roff_t st_regsize;
  The size of the mutex region, in bytes.
u_int32_t st_region_wait;
  The number of times that a thread of control was forced to wait before obtaining the mutex region mutex.
u_int32_t st_region_nowait;
  The number of times that a thread of control was able to obtain the mutex region mutex without waiting.

The DbEnv::mutex_stat method may not be called before the DbEnv::open method has been called.

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.

### Parameters

flags
  The flags parameter must be set to 0 or the following value:
  DB_STAT_CLEAR
    Reset statistics after returning their values.
statp
  The statp parameter references memory into which a pointer to the allocated statistics structure is copied.

### Errors

The DbEnv::mutex_stat method may fail and throw DbException, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:

EINVAL
  An invalid flag value or parameter was specified.

### Description: DbEnv::mutex_stat_print

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 DbEnv::set_msgfile method for more information), or passed to an application callback function (see the DbEnv::set_msgcall method for more information).

The DbEnv::mutex_stat_print method may not be called before the DbEnv::open method has been called.

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.

### Parameters

flags
  The flags parameter must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values:
  DB_STAT_ALL
    Display all available information.
  DB_STAT_CLEAR
    Reset statistics after displaying their values.

### Class

DbEnv

### See Also

Database Environments and Related Methods`

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