DB_ENV->lock_stat()
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## DB_ENV->lock_stat()

    #include <db.h>

    int
    DB_ENV->lock_stat(DB_ENV *env, DB_LOCK_STAT **statp, u_int32_t flags);

The `DB_ENV->lock_stat()` method returns the locking subsystem statistics.

The `DB_ENV->lock_stat()` method creates a statistical structure of type DB_LOCK_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 DB_ENV->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_LOCK_STAT fields will be filled in:

- u_int32_t st_id;

  The last allocated locker ID.

- u_int32_t st_cur_maxid;

  The current maximum unused locker ID.

- int st_nmodes;

  The number of lock modes.

- u_int32_t st_maxlocks;

  The maximum number of locks possible.

- u_int32_t st_maxlockers;

  The maximum number of lockers possible.

- u_int32_t st_maxobjects;

  The maximum number of lock objects possible.

- u_int32_t st_partitions;

  The number of lock table partitions.

- u_int32_t st_nlocks;

  The number of current locks.

- u_int32_t st_maxnlocks;

  The maximum number of locks at any one time. Note that if there is more than one partition, this is the sum of the maximum across all partitions.

- u_int32_t st_maxhlocks;

  The maximum number of locks in any hash bucket at any one time.

- uintmax_t st_locksteals;

  The maximum number of locks stolen by an empty partition.

- uintmax_t st_maxlsteals;

  The maximum number of lock steals for any one partition.

- u_int32_t st_nlockers;

  The number of current lockers.

- u_int32_t st_maxnlockers;

  The maximum number of lockers at any one time.

- u_int32_t st_nobjects;

  The number of current lock objects.

- u_int32_t st_maxnobjects;

  The maximum number of lock objects at any one time. Note that if there is more than one partition this is the sum of the maximum across all partitions.

- u_int32_t st_maxhobjects;

  The maximum number of objects in any hash bucket at any one time.

- uintmax_t st_objectsteals;

  The maximum number of objects stolen by an empty partition.

- uintmax_t st_maxosteals;

  The maximum number of object steals for any one partition.

- uintmax_t st_nrequests;

  The total number of locks requested.

- uintmax_t st_nreleases;

  The total number of locks released.

- uintmax_t st_nupgrade;

  The total number of locks upgraded.

- uintmax_t st_ndowngrade;

  The total number of locks downgraded.

- uintmax_t st_lock_wait;

  The number of lock requests not immediately available due to conflicts, for which the thread of control waited.

- uintmax_t st_lock_nowait;

  The number of lock requests not immediately available due to conflicts, for which the thread of control did not wait.

- uintmax_t st_ndeadlocks;

  The number of deadlocks.

- db_timeout_t st_locktimeout;

  Lock timeout value.

- uintmax_t st_nlocktimeouts;

  The number of lock requests that have timed out.

- db_timeout_t st_txntimeout;

  Transaction timeout value.

- uintmax_t st_ntxntimeouts;

  The number of transactions that have timed out. This value is also a component of st_ndeadlocks, the total number of deadlocks detected.

- uintmax_t st_objs_wait;

  The number of requests to allocate or deallocate an object for which the thread of control waited.

- uintmax_t st_objs_nowait;

  The number of requests to allocate or deallocate an object for which the thread of control did not wait.

- uintmax_t st_lockers_wait;

  The number of requests to allocate or deallocate a locker for which the thread of control waited.

- uintmax_t st_lockers_nowait;

  The number of requests to allocate or deallocate a locker for which the thread of control did not wait.

- u_int32_t st_hash_len;

  Maximum length of a lock hash bucket.

- roff_t st_regsize;

  The size of the lock region, in bytes.

- uintmax_t st_part_wait;

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

- uintmax_t st_part_nowait;

  The number of times that a thread of control was able to obtain the lock partition mutex without waiting.

- uintmax_t st_part_max_wait;

  The maximum number of times that a thread of control was forced to wait before obtaining any one lock partition mutex.

- uintmax_t st_part_max_nowait;

  The number of times that a thread of control was able to obtain any one lock partition mutex without waiting.

- uintmax_t st_region_wait;

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

- uintmax_t st_region_nowait;

  The number of times that a thread of control was able to obtain the lock region mutex without waiting.

The `DB_ENV->lock_stat()` method may not be called before the DB_ENV->open() method is called.

The `DB_ENV->lock_stat()` method returns a non-zero error value on failure and 0 on success.

### Parameters

#### statp

The statp parameter references memory into which a pointer to the allocated statistics structure is copied.

#### flags

The flags parameter must be set to 0 or the following value:

- `DB_STAT_CLEAR`

  Reset statistics after returning their values.

### Errors

The `DB_ENV->lock_stat()` method may fail and return one of the following non-zero errors:

#### EINVAL

An invalid flag value or parameter was specified.

### Class

DB_ENV, DB_LOCK

### See Also

Locking Subsystem and Related Methods

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