DB_ENV->set_lk_detect()
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DB_ENV->set_lk_detect()

#include <db.h>

int
DB_ENV->set_lk_detect(DB_ENV *dbenv, u_int32_t detect);

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 database environment's deadlock detector configuration may also be configured 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 method detect parameter 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.

The DB_ENV->set_lk_detect() method configures a database environment, not only operations performed using the specified DB_ENV handle.

The DB_ENV->set_lk_detect() method may be called at any time during the life of the application.

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

Parameters

detect

The detect parameter configures the deadlock detector. The specified value must be 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.

Errors

The DB_ENV->set_lk_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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DB_ENV->set_lk_conflicts()  Home  DB_ENV->set_lk_max_lockers()