DB_ENV->lock_detect()
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## DB_ENV->lock_detect()

    #include <db.h>

    int
    DB_ENV->lock_detect(DB_ENV *env,
        u_int32_t flags, u_int32_t atype, int *rejected);

The `DB_ENV->lock_detect()` method runs one iteration of the deadlock detector. The deadlock detector traverses the lock table and marks one of the participating lock requesters for rejection in each deadlock it finds.

The `DB_ENV->lock_detect()` method is the underlying method used by the db_deadlock utility. See the db_deadlock utility source code for an example of using `DB_ENV->lock_detect()` in a IEEE/ANSI Std 1003.1 (POSIX) environment.

The `DB_ENV->lock_detect()` method returns a non-zero error value on failure and 0 on success.

### Parameters

#### rejected

If the rejected parameter is non-NULL, the memory location to which it refers will be set to the number of lock requests that were rejected.

#### atype

The atype parameter specifies which lock request(s) to reject. It must be set to one of the following list:

- `DB_LOCK_DEFAULT`

  Use whatever lock policy was specified when the database environment was created. If no lock policy has yet been specified, set the lock policy to DB_LOCK_RANDOM.

- `DB_LOCK_EXPIRE`

  Reject lock requests which have timed out. No other deadlock detection is performed.

- `DB_LOCK_MAXLOCKS`

  Reject the lock request for the locker ID with the most locks.

- `DB_LOCK_MAXWRITE`

  Reject the lock request for the locker ID with the most write locks.

- `DB_LOCK_MINLOCKS`

  Reject the lock request for the locker ID with the fewest locks.

- `DB_LOCK_MINWRITE`

  Reject the lock request for the locker ID with the fewest write locks.

- `DB_LOCK_OLDEST`

  Reject the lock request for the locker ID with the oldest lock.

- `DB_LOCK_RANDOM`

  Reject the lock request for a random locker ID.

- `DB_LOCK_YOUNGEST`

  Reject the lock request for the locker ID with the youngest lock.

#### flags

The flags parameter is currently unused, and must be set to 0.

### Errors

The `DB_ENV->lock_detect()` method may fail and return one of the following non-zero errors:

#### EINVAL

An invalid flag value or parameter was specified.

### Class

DB_ENV, DB_LOCK

### See Also

Locking Subsystem and Related Methods

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