And, yes, I did read the fine manual. Honest.
What's the current "guideline" WRT Oracle's memory structures as a percent of the database server's physical RAM?
For instance, if I have an Exadata compute node with 256Gb of RAM, how much of that physical RAM can I realistically / safely use?
I know in days past, Oracle's recommendation used to be 50% of total RAM, but I'm pretty sure that the operating system doesn't need 128Gb of RAM, etc.
I'm thinking that a rough guideline of 75% should be plenty with the Exadata comp nodes:
- with 72Gb RAM - 54Gb of RAM allocated to database instance SGA / PGAs with 18Gb left.
- with 256Gb RAM - 192Gb of RAM allocated to database instance SGA / PGAs with 64Gb of RAM left.
This gives some breathing room in case the PGAs get hungry and grab more than PGA_AGGREGATE_TARGET, but doesn't waste all of that lovely, expensive memory.
Thoughts?
Mark