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db_deadlock(1)            BSD General Commands Manual           db_deadlock(1)

NAME
     db_deadlock

SYNOPSIS
     db_deadlock [-Vv] [-a e | m | n | o | w | y] [-h home] [-L file] [-t sec.usec]

DESCRIPTION
     The db_deadlock utility traverses the database environment lock region, and aborts a lock request each
     time it detects a deadlock or a lock request that has timed out. By default, in the case of a deadlock,
     a random lock request is chosen to be aborted.

     This utility should be run as a background daemon, or the underlying Berkeley DB deadlock detection
     interfaces should be called in some other way, whenever there are multiple threads or processes access-ing accessing
     ing a database and at least one of them is modifying it.

     The options are as follows:

     -a
        When a deadlock is detected, abort the locker:

        m  with the greatest number of locks

        n  with the fewest number of locks

        o  with the oldest locker ID

        w  with the fewest number of write locks

        y  with the youngest locker ID

        When lock or transaction timeouts have been specified:

        e  abort any lock request that has timed out

     -h
        Specify a home directory for the database environment; by default, the current working directory is
        used.

     -L
        Log the execution of the db_deadlock utility to the specified file in the following format, where
        ### is the process ID, and the date is the time the utility was started.

              db_deadlock: ### Wed Jun 15 01:23:45 EDT 1995

        This file will be removed if the db_deadlock utility exits gracefully.

     -t
        Check the database environment every sec seconds plus usec microseconds to see if a process has been
        forced to wait for a lock; if one has, review the database environment lock structures.

     -V
        Write the library version number to the standard output, and exit.

     -v
        Run in verbose mode, generating messages each time the detector runs.

     If the -t option is not specified, db_deadlock will run once and exit.

     The db_deadlock utility uses a Berkeley DB environment (as described for the -h option, the environment
     variable DB_HOME, or because the utility was run in a directory containing a Berkeley DB environment).
     In order to avoid environment corruption when using a Berkeley DB environment, db_deadlock should
     always be given the chance to detach from the environment and exit gracefully. To cause db_deadlock to
     release all environment resources and exit cleanly, send it an interrupt signal (SIGINT).

     The db_deadlock utility does not attempt to create the Berkeley DB shared memory regions if they do not
     already exist. The application which creates the region should be started first, and then, once the
     region is created, the db_deadlock utility should be started.

     The DB_ENV->lock_detect method is the underlying method 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_deadlock utility exits 0 on success, and >0 if an error occurs.

ENVIRONMENT
     DB_HOME  If the -h option is not specified and the environment variable DB_HOME is set, it is used as
              the path of the database home, as described in DB_ENV->open.

SEE ALSO
     db_archive(1), db_checkpoint(1), db_dump(1), db_load(1), db_printlog(1), db_recover(1), db_stat(1),
     db_upgrade(1), db_verify(1)

Darwin                         December 3, 2003                         Darwin