Re: Oracle with multiple CPUs

In article <8pjck2$4qh$1_at_nnrp1.deja.com>,   gdas_at_my-deja.com wrote:
> Hi, I apologize if these questions seem basic...
>
> We currently have an Oracle test/development database running on a
> single processor Windows NT Server. We have a new machine coming soon
> which is a dual processor NT box, but is expandable to up to 4 CPUs.
 I
> am hoping to move the database to this new machine and I am trying to
> assess what I will need to do in order for oracle to take advantage of
> the additional processor. I have 3 specific questions:
>
> 1. Will I need to change/set any of the init.ora parameters?
> 2. Currently none of my tables were created using any specified
 degree
> of parallelism. If I migrate the data to the new instance as is
> (without any degree of parallelism) and don't change the application
> code at all to send parallel hints, will I still see some benefit from
> the additional processor?
> 3. Can I use parallel hints in SQL, even if the underlying tables
 were
> not created with any parallel clause?
>
> Thanks in advance for any tips,
>
> Gavin
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>

I think everyone has already talked about parallel query, But I would also point out a few other items:

• Make sure cpu_count is correctly. This is automatically set, but if you have specified something in your init file look at this.
• If you have 4 concurrent querys and 4 CPUS, each will effectively get its own processor.
• Look at little if you use parallelism to do inserts/loads. If you do, inserts all go above the highwater mark. So if yo are doing a lot of deletes and direct inserts, you may see your table allocations become quite large with 'bubbles' in them.
• Avoid setting degrees at the table/index level. I find that this in many cases causes exactly the wrong things to happen and usually performance degrades.
• The way the redo log buffer and dbwr(s) work (faster) is different with multiple processors. My opinion is that 2 200 mhz processors yield better overall performance (with many concurrent activities) than 1 400 mhz. However, I have yet to validate this with testing. I would be interested in hearing opinions on this.

HTH........

--
Doug Coan
Oracle Certified Professional DBA


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