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 either before or after environment open, but once it is set it may not be changed again during the environment's lifetime.

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 deadlock detector will reject the lock request with the lowest priority. If multiple lock requests have the lowest priority, then the detect parameter is used to select which of those lock requests to reject. 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