Initialization Parameters, 46 of 188

ENQUEUE_RESOURCES

Parameter type:
Integer

Parameter class:
Static

Default value:
Derived from SESSIONS parameter

Range of values:
10 to unlimited

ENQUEUE_RESOURCES sets the number of resources that can be concurrently locked by the lock manager. An enqueue is a sophisticated locking mechanism that permits several concurrent processes to share known resources to varying degrees. Any object that can be used concurrently can be protected with enqueues. For example, Oracle allows varying levels of sharing on tables: two processes can lock a table in share mode or in share update mode.

One difference between enqueues and latches is that latches do not entail an ordered queue of waiting processes as do enqueues. Processes waiting for latches can either use timers to wake up and retry or (in multiprocessors) spin.
The default value of ENQUEUE_RESOURCES is derived from the SESSIONS parameter and is usually adequate, as long as its value is greater than DML_LOCKS + 20. For three or fewer sessions, the default value is 20. For 4 to 10 sessions, the default value is ((SESSIONS - 3) * 5) + 20. For more than 10 sessions, it is ((SESSIONS - 10) * 2) + 55.

If you explicitly set ENQUEUE_RESOURCES to a value higher than DML_LOCKS + 20, then Oracle uses the value you provide.

Caution: Increase this parameter only if Oracle returns an error specifying that enqueues are exhausted. If you have many shared resources, increase the value to one per resource (regardless of the number of sessions or cursors using that resource), not one per lock.

See Also:

Oracle8i Parallel Server Administration, Deployment, and Performance.

Oracle8i Concepts.

Oracle8i Distributed Database Systems.

Parameter type:	Integer
Parameter class:	Static
Default value:	Derived from `SESSIONS` parameter
Range of values:	10 to unlimited
`ENQUEUE_RESOURCES` sets the number of resources that can be concurrently locked by the lock manager. An enqueue is a sophisticated locking mechanism that permits several concurrent processes to share known resources to varying degrees. Any object that can be used concurrently can be protected with enqueues. For example, Oracle allows varying levels of sharing on tables: two processes can lock a table in share mode or in share update mode.
One difference between enqueues and latches is that latches do not entail an ordered queue of waiting processes as do enqueues. Processes waiting for latches can either use timers to wake up and retry or (in multiprocessors) spin. The default value of `ENQUEUE_RESOURCES` is derived from the `SESSIONS` parameter and is usually adequate, as long as its value is greater than `DML_LOCKS` + 20. For three or fewer sessions, the default value is 20. For 4 to 10 sessions, the default value is ((`SESSIONS` - 3) * 5) + 20. For more than 10 sessions, it is ((`SESSIONS` - 10) * 2) + 55.
If you explicitly set `ENQUEUE_RESOURCES` to a value higher than `DML_LOCKS` + 20, then Oracle uses the value you provide.
Caution: Increase this parameter only if Oracle returns an error specifying that enqueues are exhausted. If you have many shared resources, increase the value to one per resource (regardless of the number of sessions or cursors using that resource), not one per lock.
See Also: Oracle8i Parallel Server Administration, Deployment, and Performance. Oracle8i Concepts. Oracle8i Distributed Database Systems.