Memory Sizing Advice

I'm in the process of speccing out the hardware for an Oracle 10.2.0.3 server. We're expecting a database in the 200G size. Working set is hard to estimate, but in analagous 100G systems I see a buffer hit ratio or around 70% with a 2.3 G SGA (about as big as I can get it on a 32 bit OS). Based on this and a fair amount of spitball analysis I'd guess the working set on the new box to be around 8-10G.

For the new hardware, we're going to 64bit os, and 64 bit Oracle. We're expecting 50 or so concurrent connections to the database (all coming from an application pool). Given the nature of the application though, its very unusual for the acutal concurrency to get much over 15 or so active sessions.

The question I have is, is there any downside to me buying, say, a 32G box and setting the SGA size at 20G? Will I actually end up harming my performance with an over-large SGA (assuming I have enough physical memory to keep the box out of swap)? Received on Thu May 08 2008 - 22:07:25 CDT