enq: TX - contention
Enqueue wait. Transaction.
Additional Information​
An enqueue is a wait for a resource held by another.
enq: TX - contention is a transaction related enqueue. This can be another session waiting on row level locks to be released by either a commit or rollback. The object in question may be a table or an index.
How to reduce this wait​
Examine application logic to check for multiple updated to the records in the same block.
ASH reports will not always show the problem SQL, as the locking session may be very brief and not be active when the stats are gathered. These cases are difficult to diagnose.
Ali Kapar’s blog “enq tx – row lock contention and p1 value analyze” gives techniques to help diagnose the locking issues.
On ORA-600.pl, “THE CURIOUS CASE OF ENQ: TX – ROW LOCK CONTENTION” shows that a case, enq: TX - contention was caused by introduction of network latency after a migration to a remote location.
Additional Links​
Oracle Docs - Oracle Enqueue Names
Ali Kapar’s blog - enq tx – row lock contention and p1 value analyze
ORA-600.pl - THE CURIOUS CASE OF ENQ: TX – ROW LOCK CONTENTION
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