Berkeley DB: DB_ENV->set_lk_detect
Description: Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++

### DB_ENV->set_lk_detect |

`

###

    #include <db.h>

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

    int
    DB_ENV->get_lk_detect(DB_ENV *dbenv, u_int32_t *lk_detectp);

### Description: DB_ENV->set_lk_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 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 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.

Although the DB_ENV->set_lk_detect method may be called at any time during the life of the application, it should normally be called before making calls to the db_env_create or db_create methods.

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
  If the method was called after DB_ENV->open was called; or if an invalid flag value or parameter was specified.

### Description: DB_ENV->get_lk_detect

The DB_ENV->get_lk_detect method returns the deadlock detector configuration.

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

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

### Parameters

lk_detectp
  The DB_ENV->get_lk_detect method returns the deadlock detector configuration in lk_detectp.

### Class

DB_ENV, DB_LOCK

### See Also

Locking Subsystem and Related Methods`

Copyright (c) 1996-2004 Sleepycat Software, Inc. - All rights reserved.