Did I Misunderstand Sizing Rule Of Thumb?

A while back I was given a sizing rule of thumb which I've been using to date since I've not had time to do any proper performance analysis (blame the guy that sets my schedule!).

The rule was:

1. SGA should be about a third of physical memory
2. The Shared Pool should be about 10 times the size of the Buffer Cache

I'm increasing suspicious that I misheard this as I seem to be wasting a lot of resources. In particular, with Rule 2 surely the buffer cache should be bigger - isn't the overhead of fetching data to memory more than doing some extra parsing?

In my particular case the main application that runs on the database is a generic application using ODBC without any bind variables - what impact should that make on a sizing plan for the shared pool?

Any advice would be much appreciated.

Thanks,

• Bill.