Causes for "Enq: TM - contention" on a table with conventional path insert?
- From: David Aldridge <david@xxxxxxxxxxxxxxxxxx>
- To: Oracle List <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 15 May 2008 13:17:53 -0700 (PDT)
Folks,
I have a situation like this:
10.2.0.2 EE on Sparc 64bit
An insert statement of the form ...
INSERT INTO target_table
(...)
SELECT /*+ ORDERED FULL (t1) FULL(t2) FULL(t3) */
...
FROM t1, t2, t3, t4
WHERE t1.col1 = t2.col2
AND t1.col3 = t3.col4
AND t1.col1 >= :b2
AND t1.col1 < :b1
/
The target table is range partitioned with 8 ranges, and 8 copies of the above
query run simultaneously to load the table using different :b1 and :B2 values.
Each statement loads a single partition but the optimizer has no way of
deducing that fact. (Not my design!)
There are no indexes on the table at the time of load.
There are no constraints on the table at all.
Oracle is serializing the inserts so that only one session can insert into the
target table at a time. I would expect this if I was performing direct path
load, maybe if there were bitmap indexes, or if there were FK's involved
perhaps, but I've ruled out all of those.
V$SESSION_WAIT shows the following:
SID: 394
SEQ#: 79
Event: enq: TM - contention
P1TEXT: name|mode
...
P1RAW: 00000000544D0006 -- ie. a TM Exclusive?
.. and the P2 parameter gives the object_id for the target table in the insert
statement
So I'm a bit at a loss to know what else could cause this, or what tests to run
next time i execute this process in order to get more data to help analyze it.
Thoughts?
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