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09.13.2005 at 09:49AM PDT, ID: 21559936
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Locking a table with the "NO WAIT" option

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9.8
Zone:

Oracle Database

Tags:

oracle, wait, nowait
Is there a way to lock a table in Oracle 9/10 so that when another process tries to access/lock the table, the current lock tells the new process to not wait for the lock to lift?  I need to run a long update on a table (without taking the database down entirely) and I want any transactions that hit the table while the update is running to bounce with a "table is locked" type error.

According to the Oracle SQL Reference, it seems that "NO WAIT" option on a lock command only pertains to the lock being set, not any new incoming locks.

"Specify NOWAIT if you want Oracle to return control to you immediately if the specified table (or specified partition or subpartition) is already locked by another user. In this case, Oracle returns a message indicating that the table, partition, or subpartition is already locked by another user."

Example:
Update A locks table x (LOCK TABLE x IN EXCLUSIVE MODE) and starts updating.
Process B tries to perfom an update command (with a ROW SHARE lock).
Process B encounters the lock from A and returns a message (TABLE x LOCKED) instead of waiting for A's lock to lift.

If I read the SQL Ref. correctly, I would have to specify the "NO WAIT" option in the lock that Process B uses. I'm trying to do it the other way around since changing the sql statements on Processes B-etc. is not realistic for this one time data update.
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Answered By: markgeer
Expert Since: 01/08/1999
Accepted Solutions: 2368
Computer Expertise: Advanced
markgeer has been an Expert for 10 years, during which he has posted 9834 comments and answered 2368 questions. markgeer is just one of 1067 experts in the Oracle Database Zone. 1 expert collaborated on this answer, which was graded an "A" by the asker.
 
 
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