Oracle Database Discussions

PX Deq Credit: send blkd At Top 5 Timed Events

Hi ,
Below are examples of "Top 5 Timed Events" in my Staging data warehouse database.
ALWAYS , at the most Top 5 Timed Events is the event : PX Deq Credit: send blkd.
Oracle saids that its an idel event, but since it always at the the top of my AWR reports
and all the others events are far behind it , i have a feeling that it may indicate of
a problem.

Top 5 Timed Events Avg %Total
~~~~~~~~~~~~~~~~~~ wait Call
Event Waits Time (s) (ms) Time Wait Class
------------------------------ ------------ ----------- ------ ------ ----------
PX Deq Credit: send blkd 3,152,038 255,152 81 95.6 Other
direct path read 224,839 4,046 18 1.5 User I/O
CPU time 3,217 1.2
direct path read temp 109,209 2,407 22 0.9 User I/O
db file scattered read 31,110 1,436 46 0.5 User I/O
-------------------------------------------------------------

Top 5 Timed Events Avg %Total
~~~~~~~~~~~~~~~~~~ wait Call
Event Waits Time (s) (ms) Time Wait Class
------------------------------ ------------ ----------- ------ ------ ----------
PX Deq Credit: send blkd 6,846,579 16,359 2 50.4 Other
direct path read 101,363 5,348 53 16.5 User I/O
db file scattered read 105,377 4,991 47 15.4 User I/O
CPU time 3,795 11.7
direct path read temp 70,208 940 13 2.9 User I/O
-------------------------------------------------------------

Hir some more information:
Its a 500GB database on linux Red hat 4 with 8 CPUs and 16GB memory.
Its based on an ASM file system.

From the spfile:
SQL> show parameter parallel

NAME_COL_PLUS_SHOW_PARAM VALUE_COL_PLUS_SHOW_PARAM
------------------------------ ------------------------------
parallel_adaptive_multi_user TRUE
parallel_automatic_tuning FALSE
parallel_execution_message_size 4096
parallel_instance_group
parallel_max_servers 240
parallel_min_percent 0
parallel_min_servers 0
parallel_server FALSE
parallel_server_instances 1
parallel_threads_per_cpu 2
recovery_parallelism 0

Thanks.