Berkeley DB: DB_ENV->lock_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++

DB_ENV->lock_stat |

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    #include <db.h>

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

    int
    DB_ENV->lock_stat_print(DB_ENV *env, u_int32_t flags);

Description: DB_ENV->lock_stat

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.

u_int32_t 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.

u_int32_t st_locksteals;

- The maximum number of locks stolen by for an empty partition.

u_int32_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.

u_int32_t st_objectsteals;

- The maximum number of objects stolen by for an empty partition.

u_int32_t st_maxosteals;

- The maximum number of object steals for any one partition.

u_int32_t st_nrequests;

- The total number of locks requested.

u_int32_t st_nreleases;

- The total number of locks released.

u_int32_t st_nupgrade;

- The total number of locks upgraded.

u_int32_t st_ndowngrade;

- The total number of locks downgraded.

u_int32_t st_lock_wait;

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

u_int32_t st_lock_nowait;

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

u_int32_t st_ndeadlocks;

- The number of deadlocks.

u_int32_t st_locktimeout;

- Lock timeout value.

u_int32_t st_nlocktimeouts;

- The number of lock requests that have timed out.

u_int32_t st_txntimeout;

- Transaction timeout value.

u_int32_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.

u_int32_t st_objs_wait;

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

u_int32_t st_objs_nowait;

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

u_int32_t st_lockers_wait;

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

u_int32_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.

u_int32_t st_part_wait;

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

u_int32_t st_part_nowait;

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

u_int32_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.

u_int32_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.

u_int32_t st_region_wait;

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

u_int32_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
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 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.

Description: DB_ENV->lock_stat_print

The DB_ENV->lock_stat_print method displays the locking subsystem statistical information, as described for the DB_ENV->lock_stat method. The information is printed to a specified output channel (see the DB_ENV->set_msgfile method for more information), or passed to an application callback function (see the DB_ENV->set_msgcall method for more information).

The DB_ENV->lock_stat_print method may not be called before the DB_ENV->open method is called.

The DB_ENV->lock_stat_print method returns a non-zero error value on failure and 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.
  DB_STAT_LOCK_CONF
  - Display the lock conflict matrix.
  DB_STAT_LOCK_LOCKERS
  - Display the lockers within hash chains.
  DB_STAT_LOCK_OBJECTS
  - Display the lock objects within hash chains.
  DB_STAT_LOCK_PARAMS
  - Display the locking subsystem parameters.

Class DB_ENV, DB_LOCK
See Also Locking Subsystem and Related Methods`

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