High (?) memory usage
Hi,
we are doing some performance work on an Oracle 10.2.0.4 database. There is quite a number of legacy problems there, but I would like to ask about something else.
The database is living on a 32-CPU box with 125 Gb of RAM (the OS is SPARC Solaris 10). While CPU utilization seems fine (40-50%), memory usage looks kinda high: most of the time it's between 80 and 90% (SGA 85 Gb + PGA 15 Gb + small contribution from non-Oracle processes). Actually, I'm not sure if it qualifies as "high": on one hand, 90% does seem to be a lot, and when my home PC is reaching this level of memory utilization everything becomes much slower. On the other hand, it's not my home PC: there are still over 10 Gb of RAM left, which is probably more than enough for all OS kernel processes...
So my question is: if there is a budget for some additional hardware capacity, is it worth it investing in memory? Will it provide any performance benefits (assuming that both SGA and PGA are big enough and don't need increasing)? Is 10-20 Gb enough "head room" for the OS on a server like this? And in general, are there any "rules of the thumb" here to tell us what memory utilization level is acceptable on a database server?
Thanks in advance!
Best regards,
Nikolay