cpu_count per instance in a hard partition

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.

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