Hmm . . . last I checked, 25% of 3600 was 900, but I'm being picky. As Cary Millsap (Optimizing Oracle Performance) points out, it is hard to predict where the bottlenecks are. Either scaling up or down. Offhand I would guess that you are probably close if it is just an OLTP application. But are there critical batch jobs involved? Do vendors still offer benchmarks? You could prepare a benchmark that represents your goal and then execute it on the hardware configuration you propose to purchase. Or figure a disaster will never occur, so just take a S.W.A.G. at it.