Parallel query issue

Question

red hat
11.1.0.6.0 db
Hi,
i am trying to run update statement in parallel, but while checking the contents of tables i monitor during that update statement execution,
it seems that no parallel operation is done.
SQL> sho parameter parallel
NAME                                 TYPE        VALUE
fast_start_parallel_rollback         string      LOW
parallel_adaptive_multi_user         boolean     TRUE
parallel_automatic_tuning            boolean     FALSE
parallel_execution_message_size      integer     2152
parallel_instance_group              string
parallel_io_cap_enabled              boolean     FALSE
parallel_max_servers                 integer     8
parallel_min_percent                 integer     0
parallel_min_servers                 integer     4
parallel_server                      boolean     FALSE
parallel_server_instances            integer     1
NAME                                 TYPE        VALUE
parallel_threads_per_cpu             integer     2
recovery_parallelism                 integer     01.
SQL> alter session enable parallel dml;
Session altered.2.
SQL> update /*+ PARALLEL tablex,8) */  tablex set colx = 1;
113485 rows updated.
Elapsed: 00:00:07.47during this 7 seconds of update statement execution,
i'm running the following sql's with the same user from antoher session :
SQL> r
  1* select * from v$px_session
no rows selected
SQL> select pid, status, server_name from v$px_process;
       PID STATUS    SERV
        23 AVAILABLE P000
        29 AVAILABLE P003
        24 AVAILABLE P001
        25 AVAILABLE P002
SQL> SELECT dfo_number, tq_id, server_type, process, num_rows, bytes
  2  FROM v$pq_tqstat
  3  ORDER BY dfo_number DESC, tq_id, server_type DESC , process;
no rows selected
....So ,is it true that this update is not executing in parallel ?
any comments are welcome.
thanks.

Answer 1

The question is: Are you looking for a "parallel query" or a "parallel dml" operation? The thread subject suggests the former, your example enabling "parallel dml" the latter.
The plan posted is not a "parallel dml" plan. See the difference:
Parallel Query only:
| Id  | Operation             | Name     | Rows  | Bytes | Cost (%CPU)| Time     |    TQ  |IN-OUT| PQ Distrib |
|   0 | UPDATE STATEMENT      |          |    32 |   448 |     2   (0)| 00:00:01 |        |      |            |
|   1 |  UPDATE               | ABC      |       |       |            |          |        |      |            |
|   2 |   PX COORDINATOR      |          |       |       |            |          |        |      |            |
|   3 |    PX SEND QC (RANDOM)| :TQ10000 |    32 |   448 |     2   (0)| 00:00:01 |  Q1,00 | P->S | QC (RAND)  |
|   4 |     PX BLOCK ITERATOR |          |    32 |   448 |     2   (0)| 00:00:01 |  Q1,00 | PCWC |            |
|   5 |      TABLE ACCESS FULL| ABC      |    32 |   448 |     2   (0)| 00:00:01 |  Q1,00 | PCWP |            |
---------------------------------------------------------------------------------------------------------------Parallel Query + Parallel DML (enabled):
| Id  | Operation             | Name     | Rows  | Bytes | Cost (%CPU)| Time     |    TQ  |IN-OUT| PQ Distrib |
|   0 | UPDATE STATEMENT      |          |    32 |   448 |     2   (0)| 00:00:01 |        |      |            |
|   1 |  PX COORDINATOR       |          |       |       |            |          |        |      |            |
|   2 |   PX SEND QC (RANDOM) | :TQ10000 |    32 |   448 |     2   (0)| 00:00:01 |  Q1,00 | P->S | QC (RAND)  |
|   3 |    UPDATE             | ABC      |       |       |            |          |  Q1,00 | PCWP |            |
|   4 |     PX BLOCK ITERATOR |          |    32 |   448 |     2   (0)| 00:00:01 |  Q1,00 | PCWC |            |
|   5 |      TABLE ACCESS FULL| ABC      |    32 |   448 |     2   (0)| 00:00:01 |  Q1,00 | PCWP |            |
---------------------------------------------------------------------------------------------------------------Regards,
Randolf
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