Another issue that gets a lot of attention is whether you should run 32-bit or 64-bit Oracle on your 64-bit UNIX. At first this sounds like a dumb question, right? But for some of the platforms, the answer may very well surprise you. For example, Oracle's Metalink technical support site quotes that:
32-bit Oracle on HP-UX 11.00 32-bit—No difference
32-bit Oracle on HP-UX 11.00 64-bit—1–2% degradation
64-bit Oracle on HP-UX 11.00 64-bit—8–9% degradation
And here I thought that 64-bit was always faster. The point is: Know your target platform and its Oracle ports. Don't just assume that bigger is better.
Then there's the ever-popular question of the maximum system-wide SGA size limit of 32-bit versus 64-bit Oracle. ...