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

# DbEnv::lock_stat |

`

###

    #include <db_cxx.h>

    extern "C" {
    	typedef void *(*db_malloc_fcn_type)(size_t);
    };
    int
    DbEnv::lock_stat(DB_LOCK_STAT **statp, db_malloc_fcn_type db_malloc);

# Description

The DbEnv::lock_stat method creates a statistical structure and copies a pointer to it into a user-specified memory location.

Statistical structures are created in allocated memory. If db_malloc is non-NULL, it is called to allocate the memory, otherwise, the library function malloc(3) is used. The function db_malloc must match the calling conventions of the malloc(3) library routine. Regardless, the caller is responsible for deallocating the returned memory. To deallocate returned memory, free the returned memory reference, references inside the returned memory do not need to be individually freed.

The lock region statistics are stored in a structure of type DB_LOCK_STAT. The following DB_LOCK_STAT fields will be filled in:

u_int32_t st_lastid;
  The last allocated lock 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_nlockers;
  The number of current lockers.
u_int32_t st_maxnlockers;
  The maximum number of lockers 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_nnowaits;
  The total number of lock requests that failed because DB_LOCK_NOWAIT was set.
u_int32_t st_nconflicts;
  The total number of locks not immediately available due to conflicts.
u_int32_t st_ndeadlocks;
  The number of deadlocks detected.
u_int32_t st_regsize;
  The size of the region.
u_int32_t st_region_wait;
  The number of times that a thread of control was forced to wait before obtaining the region lock.
u_int32_t st_region_nowait;
  The number of times that a thread of control was able to obtain the region lock without waiting.

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.

# Errors

The DbEnv::lock_stat method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods. If a catastrophic error has occurred, the DbEnv::lock_stat method may fail and either return DB_RUNRECOVERY or throw an exception encapsulating DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.

### Classes

DbEnv, DbLock

# See Also

DbEnv::set_lk_conflicts, DbEnv::set_lk_detect, DbEnv::set_lk_max, DbEnv::lock_detect, DbEnv::lock_get, DbEnv::lock_id, DbLock::put, DbEnv::lock_stat and DbEnv::lock_vec.`

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