You can have 1 or 2 rbs in the system ts and atleast 4 rbs in the RBS ts. #rbs required = #users/transactions_per_rbs --> this should be rounded to the next higher multiple of 4. Do not wait for users to complain.
I didn't realize that you should/would create more rollback segments in the same tablespace that was used for the first non-system rollback segment. Is it a benefit to create another tablespace dedicated for the 2nd non-system rollback segment ?
What about increasing the size of the tablespace used by the original rollback segment ? Would that be a substitute for created the 2nd one ?
Yes- I have read a bit about rollback segments- it's still a bit difficult.
You need not create another ts for the new rbs; you can create it in the same rbs. The size of the ts would depend upon the # rbs and their sizes (based upon the transaction size --> which depends upon if the db is OLTP or DW/DSS) you have in the ts. For now, resize the rbs dbf to say 0.5 to 1 gb. Turn on Autoextend, and create the rbs with an optimal storage parameters.
Ex. if optimal = (say) 10Mb, then set initial_extent = next_extent = 1/2 of optimal size. In this case, it would be 5Mb. Remember that extent allocation (esp for rbs) is CPU intensive.