db_deadlock [-Vvw]
    [-a m | n | o | w | y] [-h home] [-L file] [-t sec]

Description

The db_deadlock utility traverses the database lock structures, and aborts a lock request each time it detects a deadlock. By default, 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 accessing 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

-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 to see if a process has been forced to wait for a lock; if one has, make a deadlock detection pass.

-V

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

-v

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

-w

Check the database environment every 100ms to see if a process has been forced to wait for a lock; if one has, make a deadlock detection pass.

At least one of the -t and -w options must be specified.

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_deadlock utility exits 0 on success, and >0 if an error occurs.

Environment Variables

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