Berkeley DB: DB_ENV->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++

# 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);

# Description

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

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

DB_STAT_CLEAR
  Reset statistics after returning their values.

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 created 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 library malloc(3) interface 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_nnowaits;
  The total number of lock requests failing 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.
u_int32_t st_locktimeout;
  Lock timeout value.
u_int32_t st_nlocktimeouts;
  The number of locks 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_regsize;
  The size of the lock 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 DB_ENV->lock_stat method returns a non-zero error value on failure and 0 on success.

# Errors

The DB_ENV->lock_stat method may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions. If a catastrophic error has occurred, the DB_ENV->lock_stat method may fail and return DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.

# Class

DB_ENV, DB_LOCK

# See Also

Locking Subsystem and Related Methods`

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