Berkeley DB: DbEnv::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++

### DbEnv::lock_stat |

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###

    #include <db_cxx.h>

    int
    DbEnv::lock_stat(DB_LOCK_STAT **statp, u_int32_t flags);

    int
    DbEnv::lock_stat_print(u_int32_t flags);

### Description: DbEnv::lock_stat

The DbEnv::lock_stat method returns the locking subsystem statistics.

The DbEnv::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 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_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_nlocks;
  The number of current locks.
u_int32_t st_maxnlocks;
  The maximum number of locks at any one time.
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.
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_locks_wait;
  The number of requests to allocate or deallocate a lock structure for which the thread of control waited.
u_int32_t st_locks_nowait;
  The number of requests to allocate or deallocate a lock structure 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_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 DbEnv::lock_stat method may not be called before the DbEnv::open method has been called.

The DbEnv::lock_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::lock_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::lock_stat_print

The DbEnv::lock_stat_print method displays the locking subsystem statistical information, as described for the DbEnv::lock_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::lock_stat_print method may not be called before the DbEnv::open method has been called.

The DbEnv::lock_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.
  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

DbEnv, DbLock

### See Also

Locking Subsystem and Related Methods`

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