EXPERT RESPONSE
Rather than attempt to calculate your processes parameter value down to an
exact figure, I would suggest using some rough guesswork on the number of
total processes per instance you expect, at least double it, and then
monitor your v$ views to adjust it if necessary. This is not extremely
memory-intensive and I typically see numbers in my MAX_UTILIZATION of 1/3 my
INITIAL_ALLOCATION in my v$resource_limit view. In other words, approach it
for each instance in the same way as you would if the instance was the sole
instance for the database. You are not required to set this uniformly across
nodes.
The value for sessions is derived from processes (*1.1 + 5, or something
like that?) and although Oracle documentation advises that this may need to
be adjusted if you manually adjust the processes parameter, I don't believe
I have ever supported a system where I have had to do this, RAC or not.
Unless your system has a particular quirk that requires you to visit this
parameter specifically, I would leave it set to the value derived from the
processes setting.
I hope this helps,
Bill
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