Re: cpu_count per instance in a hard partition

This is documented here and is basically the use case for the resource manager's instance caging feature:

https://docs.oracle.com/cd/E11882_01/server.112/e25494/dbrm.htm#CFHBDFAG

On Fri, Nov 23, 2018 at 8:55 PM Patrice sur GMail <patrice.boivin_at_gmail.com> wrote:

> Hi,
>
> a possibly dumb question:
>
> If you have a hard partition with 2 cores but 8 threads total but are
> running five Oracle instances within that hard partition, does the Oracle
> software know that five instances are running from the same home? Or is
> each instance oblivious to the fact that it is sharing resources with other
> instances.
>
> I ask because if we set cpu_count=8 in each of five instances, doesn't
> that mean the instances expect the hard partition to provide a total of 40
> threads?
>
> If they are aware of their environment then each instance could say "well
> obviously they are lying to me, I only really have 8/5 threads available to
> me, though we are sharing resources so sometimes I will have more time
> slices, other times, not as many."
>
> Overloading may not cause major problems other than each instance not
> getting as many time slices as it expects, i.e. each one would end up
> running slower than optimal. (reminds me of when I was a student working
> on an overloaded mainframe which had more dumb terminals than recommended,
> each dumb terminal had to wait for time slices) Meanwhile there would be
> nearly no wasted time slices because the CPUs are very busy.
>
> -- Patrice
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