DbEnv::mutex_stat()
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## DbEnv::mutex_stat()

    #include <db_cxx.h>

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

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.

- uintmax_t st_region_wait;

  The number of times that a thread of control was forced to wait before obtaining the mutex region mutex.

- uintmax_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 is 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 a DbException exception, 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.

### Class

DbEnv

### See Also

Mutex Methods

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