Rookie Question - Memory Usage

Good Day All,

Long time reader, first time poster :)

I am using 10g server on an aix 5.3 box. Is it normal that oracle consistently uses up all the RAM on my machine. I am constantly getting warnings from my OEM saying that memory usage is in the warning levels, always above 97%. I've added up how much the PGA/SGA should be taking up for each of the 4 instances on this machine and it's only about half of what my RAM usage is. Oracle server is the only thing running on this box. Any advice would be greatly appreciated.

• Rich