Getting ORA-00054

Question

Our application is getting the following error...
SQL> select * from cmd where CC0034_CMD_NRI = 111 for update nowait;
select * from cmd where CC0034_CMD_NRI = 111 for update nowait
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified
My understanding is that the requested record is locked and that the "FOR UPDATE NOWAIT" clause causes the error. How do I find out who locked the record ?
How do I prevent this from happening again, or is retrying until the locked record is free the only option I have ?
Thanks,
Gabriel

Answer 1

Yes this error comes from that some other users were holding a lock on a table.
Example below will demonstrate this:
Session one:
[email protected]> create table t(id int);
Table created.
[email protected]> insert into t values(10);
1 row created.
[email protected]> lock table t in exclusive mode;
Table(s) Locked.
Session two:
[email protected]> select * from t for update nowait;
select * from t for update nowait
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified
[email protected]> select * from t for update ;
still wating..........
You can peform this check:
[email protected]> select * from dba_blockers;
HOLDING_SESSION
11
to get sid of the blocking sessions and then using v$ views you can check sid, serial#, sql statetment being executed and so on..
Best Regards
Krystian Zieja / mob