# Berkeley DB: DbEnv::lock_detect
Berkeley DB: An embedded database programmatic toolkit.
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DbEnv::lock_detect |

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    #include <db_cxx.h>

    int
    DbEnv::lock_detect(u_int32_t flags, u_int32_t atype, int *rejected);

Description: DbEnv::lock_detect

The DbEnv::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 DbEnv::lock_detect 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
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 DbEnv::lock_detect 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.

Class DbEnv, DbLock
See Also Locking Subsystem and Related Methods`

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