Re: shared pool latch time out exceeding 40% HELP!!!

Hi,

I don;t know if this link will be off any interest, but I found it within Technet.

http://technet.oracle.com/support/bboard/content/672.htm

The subject is; Library Cache and Shared Pool Tuning, and goes into Latch Contention amount others.

Andrew

Kunihito Ishibashi wrote:

> upon doing further investigation of the oracle db problem that we
> wereexperiencing
> (cpu usage exceeding 100%), we discovered that the db isnot successfully
> obtaining the "latch" necessary to perform a transaction
> (in trying to obtain the latch, oracle goes through an excessive number
> ofloops).
>
> with the spin count set to 2,000 and using oracle's estat/bstat tool,
> we obtained the below results. according to oracle's documentation, the
> xxx latch time out
> statistics should not exceed 1%. however, in our tests,the shared pool
> latch time out percentage
> reached approximately 40% (out of10 million transaction, 3.9 million of the
> transactions failed).
> referring once again to oracle's documentation, it is noted that increasing
> the shared pool
> size to 300000000 its current value should improve performance
> (in other words, reduce the shared pool latch time out percentage to a more
> reasonable percentage).
> however, making such changes did not yield any improvement.
>
> we are wondering whether this is a problem with the HP-UX B.11.00 or with
> oracle8.0.5.1.0.
>
> any feedback is appreciated. thank you...
>
> xxx LATCH TIMEOUT (oracle's estat/bstat):
> ROW_CACHE_OBJECT 5%
> SHARD_POOL 40%
> LIBRARY_CACHE 12%
> REDO_ALLOCATION 0.09%
> REDO_COPY 0.05%
>
> SERVER SPEC:
> HP-UX k580a B.11.00 E 9000/800 (th) 32bit
> CPU PA-8200 x 6
> MEMORY 2GB
> DISK EMC SYMMETRIX MODEL3430 (5GB MEMORY/800GB DISK)
> EMC POWERPATH RELEASE 1.3
> ORACLE RELEASE 8.0.5.1.0
Received on Sun May 02 1999 - 23:57:13 CDT