I want to maximize the total available memory on our UNIX box. In that regard, I have heard that the SGA should not be more than half of the total available.

Also, what about the number of users logging in, what is the per user amount of memory used up ?

So, to figure out what Oracle is using, I should add the SGA + (# of users * per user memory used) - is this accurate ?

What are your thoughts, comments, experience with memory config?