Oracle memory utilization on solaris

I'm running several instances of Oracle on a Sun running Solaris 2.6 and I'm trying to figure out how many more instances I can create on this server based on how much memory is available. I am having dificulty in determining just exactly how much memory is availble.

I have 4 Gigs of RAM with 1 Gig of swap. Usually I would merely issue "vmstat 1 10" to see how much memory is free. In this case it is telling me that 64 Megs out of 4 Gigs are free. When I issue "swap -l" I can see that I am not touching swap. When I issue "ps -eo vsz,args |grep oracle" to find out how much memory the oracle processes are using they total over 12 Gigs. So I am assuming that oracle is memory mapping data files which is accounting for the memory utilization discrepancy.

So... The 64 Million dollar question is... How does one determine how much memory each Oracle instance is really using so as to properly size the server and to calculate how much room is left for future instances?

Another thing that I noticed is that the core Oracle processes, such as ora_smon_<SID> uses up about 300 Megs each. When a connection comes in a process is spawned that looks like "oracle<SID> (LOCAL=NO)". These connection processes also report using about 300 Megs each. Is that right? Why would connection processes need that much memmory? I imagine that it is because the process forked from another process and it inherited the memory mapped data files, but it just adds to the confusion of how much real memory is being used.

Thanks to anyone who can clear up this mystery. :-)

--
David F. Newman
Oracle DBA
buzzwang_at_ourvillage.com Received on Wed Aug 04 1999 - 11:13:35 CDT