Re: Need a volunteer to test a simple script on HPUX 11i - Oracle 9.0.1

Jonathan Lewis wrote:
>
> Thanks to those who helped, and especially
> to 'Bobby' from Oracle Support who pointed
> me in the right direction.
>
> I had thought that the issue was related in
> some way to a new strategy for latching on
> the 'cache buffers chain' latches which could
> not be implemented properly by HP.
>
> In fact the numbers I was seeing were (almost)
> a coincidence, and the problem was nothing
> to do with 'cache buffers chains' at all. (Very
> good news !)
>
> The problem was related to the particular stress
> test that I was running, combined with the fact
> that the resource manager was enabled.
> (resource_manage_plan=system_plan).
>
> Under this configuration, I was (coincidentally)
> seeing exactly 2 gets on the "cas latch" for every
> get on the "cache buffers chains" latch - which
> was adding about 100% to the expected CPU
> cost of the operation. However, having
> commented out this parameter (don't try
> changing it dynamically, there is a known
> bug which may effectively hang the database)
> the gets on the cas latch disappeared, bringing
> the response time back down again.
>
> Running the same test (with and without
> resource_manager_plan) on a W2000
> system produced a different effect - there
> was no 'cas latch' activity, instead there
> was a much smaller overhead (about 5%)
> which was probably associated with latching
> on various 'resmgr%' latches.
>
> In summary then - HP does not have the
> totally catastrophic problem I thought it
> had, but the cost of using resource manager
> on HP systems could well be much larger than
> it is on other systems because of this 'cas latch'
> issue.
>
> Even then, the stress test I used may also have
> been hitting a bug at a particular point in the
> resource manager code which exaggerates the
> impact of the cas latch to ridiculous levels; so
> I've sent the sample SQL on to Oracle so that
> their developers can check what's going on
> behind it.
>
> --
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
> Now running 3-day intensive seminars
> http://www.jlcomp.demon.co.uk/seminar.html
>
> Host to The Co-Operative Oracle Users' FAQ
> http://www.jlcomp.demon.co.uk/faq/ind_faq.html
>
> Author of:
> Practical Oracle 8i: Building Efficient Databases
>
> Jonathan Lewis wrote in message
> <1012427839.7076.0.nnrp-02.9e984b29_at_news.demon.co.uk>...
> >
> >Is anyone running 9.0.1 on HP-UX 11i ?
> >
> >If so can you tell me if it has CAS latch
> >problems, or run a short test for me to
> >check whether shared hash latches work
> >better on 11i than they do on 11.0
> >
> >Thanks
> >

Ahhh... resource manager...gotta love it :-)

Its like when I tried an upgrade from 8.1.7.3 to 9.0.1.2 (as you've seen from the metalink post).

For other posters: probably wise to comment 'resource_plan=' when upgrading.

hth
connor

-- 
==============================
Connor McDonald

http://www.oracledba.co.uk

"Some days you're the pigeon, some days you're the statue..."