Re: "gc current block busy" wait in Concurrent BATCH Processes Run

  • From: Andrey Kriushin <Andrey.Kriushin@xxxxxxxx>
  • To: VIVEK_SHARMA@xxxxxxxxxxx
  • Date: Sun, 17 Feb 2008 01:42:04 +0300


Hi,
being signed to BAAG (http://www.battleagainstanyguess.com/members), I should not provide any guesses. However suggestions are not forbidden :). Especially on the diagnostics.
Presumably, you have seen the similar "Top 5" on all of the nodes. And all of the 256 jobs are "equivalent" (par ex executing the same procedure)?
Have you ever run the same workload in the "single instance" configuration? I.e. shutdown 2 of the 3 instances (or even start the instance from a separate ORACLE_HOME, which is not aware of "clusters" - $ make -f ins_rdbms.mk rac_off). Of course, you should not compare "apples with pineapples" - i.e.decrease your workload to 1/3 for this test and look at those "Top 5". Look at "concurrency" events, i.e. "latch free", "buffer busy" and some "unusual" enqueues. Well, 85 runnign jobs ("ACTIVE "sessions) on 60 (120/3=60 ?) cpu's should produce some concurrency (in the absense of IO)?
Let the load to grow (in the single instance) - x2, x3. Compare the results in single instance.
During all of this tests, please, measure the response time for one of your "equvalent" batch jobs (trace it). 

HTH
-- Andrey
PS. Hopefully, with more diagnostic info someone in the list would be able to give a conclusion instead of the guess :-). 
PPS. Those "SQL*Net break/reset to client" also look like a warning for me.
PPPS. The Method-R is not completely applicable in this case, as the goal of the tests is not specified. 

VIVEK_SHARMA wrote:

Folks

In a Benchmark Run, 256 concurrent BATCH Processes on RAC using Dedicated 
Sessions (NON-MTS) showing the following Waits:-

How is the "gc current block busy" wait to be addressed?
>From the Statspack Report (Level 7) which section gives the Objects which is incurring this wait? 
Is it the "Segments By Current Blocks Received" section OR the "Segments by CR Blocks 
Received" section?

Will share the Statspack Report, as needed.

Config:-
Oracle 10.2.0.3 on 3 Node RAC
Solaris 10

Cheers

Vivek

Statspack Report's Time Elapsed: 11.97 (mins)



Top 5 Timed Events                                                 Avg    %Total

~~~~~~~~~~~~~~~~~~                                                 wait    Call

Event                                     Waits        Time (s)    (ms)    Time

----------------------------------------- ------------ ----------- ------ ------

CPU time                                                 5,854             57.6

gc current block busy                     24,910         1,463      59     14.4

SQL*Net break/reset to client          1,075,218         1,285       1     12.6

gcs log flush sync                       103,520           511       5      5.0

gc buffer busy                             6,489           367      57      3.6

-------------------------------------------------------------



Host CPU (CPUs: 120)

~~~~~~~~ Load Average

Begin End User System Idle WIO WCPU

------- ------- ------- ------- ------- ------- --------

8.58 9.54

          8.26 15.61 76.13 0.00 1.19

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