Berkeley DB: DB_ENV->lock_detect
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_detect |

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    #include <db.h>

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

# Description

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

The atype parameter specifies which lock request(s) to reject. It must be set to one 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 greatest number of locks.
DB_LOCK_MINLOCKS
  Reject the lock request for the locker ID with the fewest number of locks.
DB_LOCK_MINWRITE
  Reject the lock request for the locker ID with the fewest number of write locks.
DB_LOCK_OLDEST
  Reject the lock request for the oldest locker ID.
DB_LOCK_RANDOM
  Reject the lock request for a random locker ID.
DB_LOCK_YOUNGEST
  Reject the lock request for the youngest locker ID.

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

The DB_ENV->lock_detect method is the underlying interface 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.

# Errors

The DB_ENV->lock_detect 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_detect 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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