ORA-000060 (deadlock) while insert

Question

Dear All,
I'm currently facing a problem:
- we are getting ORA-000060
- on trace file generated by the error, shows an INSERT operation as current operation
- The table related to the above INSERT operation has below properties:
- NO BITMAP INDEX
- The table is RANGE PARTITIONED
- A LOCALY PARTITIONED UNIQUE INDEX
- DB version is Oracle 9.2.0.6 on HPUX
My question is why an insert operation will cause deadlock (bitmap index) ?
Or it is resulted from other operation, if this is the case then why trace file show the insert operation as current operation ?
Please help.
BR
Obaid

Answer 1

Ok, according to the deadlock graph, these are TX enqueues, so, it's definitely NOT an unindexed foreign key problem. Locking due to unindexed FKs cause TM enqueue waits, not TX enqueue.
Since it's an S mode wait on TX and the statement involved is an insert, the most likely cause is overlapping unique values on the index.
Suppose you have:
create table testit(a number);
create unique index uniq_ind on testit(a);
Now, if you have two sessions inserting into testit:
session 1:
insert into testit values(1);
session 2:
insert into testit values(2);
session 1:
--the following insert statement will begin to hang, waiting for session 2 to commit or rollback
insert into testit values(2);
session 2:
--the following session will hang for three seconds, and then Oracle will detect a deadlock and session 1 will catch an ORA-00060.
insert into testit values(1);
So, if you have two concurrent sessions that overlap on the values of the uncommitted unique values, you'll see S mode TX enqueue waits.
Hope that helps,
-Mark