Re: Causes for "Enq: TM - contention" on a table with conventional path insert?

  • From: "Riyaj Shamsudeen" <riyaj.shamsudeen@xxxxxxxxx>
  • To: david@xxxxxxxxxxxxxxxxxx
  • Date: Thu, 15 May 2008 15:26:42 -0500

  1. Is it possible to modify insert statement to specify partition name ?
using bind variables, it may be possible to deduce partition name.
                 insert into target_table  partition (pname) ..

      This can be done using dynamic SQL.

 2. Are you sure insert statement is executing serially? No parallelism
involved here? I have seen few parallel DML operations acquiring exclusive
lock on the table. Trace or explain plan to see whether paralellism in play
or not?

Riyaj Shamsudeen
The Pythian Group

On Thu, May 15, 2008 at 3:17 PM, David Aldridge <david@xxxxxxxxxxxxxxxxxx>

> Folks,
> I have a situation like this:
> 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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