# DbEnv.set_lk_detect

`

###

    import com.sleepycat.db.*;

    public void set_lk_detect(int detect)
        throws DbException;

# Description

Set if the deadlock detector is to be run whenever a lock conflict occurs, and specify what lock request(s) should be rejected. As transactions acquire locks on behalf of a single locker ID, rejecting a lock request associated with a transaction normally requires the transaction be aborted. The specified value must be one of the following list:

Db.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.DB_LOCK_RANDOM.
Db.DB_LOCK_EXPIRE
  Reject lock requests which have timed out. No other deadlock detection is performed.
Db.DB_LOCK_MAXLOCKS
  Reject the lock request for the locker ID with the greatest number of locks.
Db.DB_LOCK_MINLOCKS
  Reject the lock request for the locker ID with the fewest number of locks.
Db.DB_LOCK_MINWRITE
  Reject the lock request for the locker ID with the fewest number of write locks.
Db.DB_LOCK_OLDEST
  Reject the lock request for the oldest locker ID.
Db.DB_LOCK_RANDOM
  Reject the lock request for a random locker ID.
Db.DB_LOCK_YOUNGEST
  Reject the lock request for the youngest locker ID.

The DbEnv.set_lk_detect method configures a database environment, not only operations performed using the specified DbEnv handle.

The DbEnv.set_lk_detect interface may not be called after the DbEnv.open interface is called. If the database environment already exists when DbEnv.open is called, the information specified to DbEnv.set_lk_detect must be consistent with the existing environment or an error will be returned.

The DbEnv.set_lk_detect method throws an exception that encapsulates a non-zero error value on failure.

The database environment's deadlock detector configuration may also be set using the environment's DB_CONFIG file. The syntax of the entry in that file is a single line with the string "set_lk_detect", one or more whitespace characters, and the interface detect argument as a string; for example, "set_lk_detect DB_LOCK_OLDEST". Because the DB_CONFIG file is read when the database environment is opened, it will silently overrule configuration done before that time.

# Errors

The DbEnv.set_lk_detect method may fail and throw an exception encapsulating a non-zero error for the following conditions:

EINVAL
  An invalid flag value or parameter was specified.

  Called after DbEnv.open was called.

The DbEnv.set_lk_detect method may fail and throw an exception for errors specified for other Berkeley DB and C library or system methods. If a catastrophic error has occurred, the DbEnv.set_lk_detect method may fail and throw a DbRunRecoveryException, in which case all subsequent Berkeley DB calls will fail in the same way.

# Class

DbEnv, DbLock

# See Also

Locking Subsystem and Related Methods`

Copyright Sleepycat Software