Berkeley DB: lock_stat
Description: Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,b+tree,btr ee,hash,hashing,transaction,transactions,locking,logging,access method,access me thods,java,C,C++

# lock_stat

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    #include <db.h>

    int
    lock_stat(DB_LOCKTAB *lt,
        DB_LOCK_STAT **statp, void *(*db_malloc)(size_t));

# Description

The lock_stat function creates a statistical structure and copies pointers to it into user-specified memory locations.

Statistical structure 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 the returned memory, free each returned memory pointer; pointers inside the 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_magic;
  The magic number that identifies a file as a lock file.
u_int32_t st_version;
  The version of the lock file type.
u_int32_t st_refcnt;
  The number of references to the region.
u_int32_t st_regsize;
  The size of the region.
u_int32_t st_maxlocks;
  The maximum number of locks possible.
u_int32_t st_nmodes;
  The number of lock modes.
u_int32_t st_numobjs;
  The number of unique objects locked.
u_int32_t st_nlockers;
  The number of unique lockers.
u_int32_t st_nconflicts;
  The total number of locks not immediately available due to conflicts.
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_ndeadlocks;
  The number of deadlocks detected.
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 lock_stat function returns the value of errno on failure, and 0 on success.

# Errors

If a fatal error occurs in Berkeley DB, the lock_stat function may fail and return DB_RUNRECOVERY, at which point all subsequent database calls will also return DB_RUNRECOVERY.

The lock_stat function may fail and return errno for any of the errors specified for the following Berkeley DB and C library functions: abort(3), fcntl(3), fprintf(3), getpid(3), malloc(3), and memset(3).

# See Also

lock_close, lock_detect, lock_get, lock_id, lock_open, lock_put, lock_stat, lock_unlink and lock_vec.`