Re: High CPU usage

hpuxrac wrote:
> shiva wrote:
> >
> > > Which oracle processes exactly are using more cpu than they used to?
> > Each client connection used to consume about 0.01% CPU before and
> > there were about 80 connections. Now each connection is consuming about
> > 0.25% CPU and there are about 1000 connections. We definately see more
> > connections then we saw before. (PGA was set to 256MB before and now is
> > set to 2GB)
>
> In your original post, you were comparing cpu utitlization between 2
> systems. Now you add that the old system was supporting 80 connections
> and the new one 1000 connections.
>
> Is that a significant difference that makes comparing cpu utilization a
> fairly senseless exercise?
> >> Agree. but out 1000 connections only few are active as it used to be before.

> Good tuned oracle systems are cpu bound. They have to be limited by
> something ... cpu is the resource it takes to perform work.
> >> True. But CPU usage should not exceed 90% right ;-) We need to limit this and make it use I/O or memory then CPU.

> Are these 1000 connections performing real work on a regular basis?
>>> Nope. Only few them are active.
> What kind of wait events is your system exhibiting?
>>> I'm surprised that no wait events. Even very few hard parses.

> Are users complaining about system performance or is it within acceptable norms?
>>> Users are not complaining about system performance. But when the CPU usage goes to 100% it just jamms up the database. New connections take long time or they have to wait untill cpu consumption goes down.

>
> What would the customers and end users pick if they could select 3 or 5
> things they would like to run faster?
>
> Those are the kinds of questions I would be concentrating on if I were
> you.
>
> You could submit questions about what you noticed with the kernel
> utilization to oracle and/or sun in a service request.
> I have opened a SR with both Sun and Oracle. I'm not getting much help from them yet. Will update If I learn something new from them.

> I would recommend you obtain and read Cary Millsap's book "Optimizing
> Oracle Performance".
>
> >
> > > What happens to the cpu utilization if you temporarily turn off RAC (
> > > run on one node of the cluster ONLY with cluster_database set to false
> > > for the instance you are running )?
> > We haven't done this yet. Thanks for quick response.
>
> I don't think this is an area to go into now based on your note that
> the number of connections is so different between the 2 systems.
Received on Wed Oct 11 2006 - 23:46:56 CDT