Contents
What causes row lock contention in Oracle?
This occurs when one application is updating or deleting a row that another session is also trying to update or delete. This can cause the “enq: TX – row lock contention” wait event. This wait event can be handled by having the session holding the lock perform a COMMIT or ROLLBACK.
What is index block contention?
In database management systems, block contention (or data contention) refers to multiple processes or instances competing for access to the same index or data block at the same time. In general this can be caused by very frequent index or table scans, or frequent updates.
What is the difference between row-level locking and table-level locking?
Table-level locking systems always lock entire tables. Row-level locking systems can lock entire tables if the WHERE clause of a statement cannot use an index. Row-level locking systems can lock entire tables if a high number of single-row locks would be less efficient than a single table-level lock.
What causes ENQ TX-row lock contention error?
When two sessions try to insert the same key value the second session must wait to see if an ORA-001 should be raised. This can cause the “enq: TX – row lock contention” wait event. This wait event can be handled by having the session holding the lock perform a COMMIT or ROLLBACK.
What does wait for TX enqueue in mode 6 mean?
A wait for the TX enqueue in mode 6 (P1 = 1415053318, P1RAW = 54580006) is the most common enqueue wait. (In Oracle Database 10g, the wait event name is enq: TX—row lock contention.) This indicates contention for row-level lock. This wait occurs when a transaction tries to update or delete rows that are currently locked by another transaction.
What does wait for TX enqueue in Oracle 10g mean?
(In Oracle Database 10g, the wait event name is enq: TX—row lock contention.) This indicates contention for row-level lock. This wait occurs when a transaction tries to update or delete rows that are currently locked by another transaction. This usually is an application issue.
How to avoid row lock contention in Oracle?
You can avoid row lock contention by making sure that the row is available for update beforehand with a SELECT FOR UPDATE and either WAIT X or NOWAIT, e.g: If the row is locked, you will receive an ORA-00054 which is in most cases preferable to indefinite waiting.