Real life memory limits under UNIX/Linux

  • From: "Tim Onions" <att755@xxxxxxxxxxx>
  • To: Oracle-L@xxxxxxxxxxxxx
  • Date: Thu, 09 Jun 2005 17:53:39 +0100

Dear All

I'm looking for a little guidance. Having lived (suffered) as an Oracle DBA 
on Windows 2000/2003 32bit for too long I'm now proposing to the board we 
should move to a "proper" environment. My main gripe with Windows is the 
memory architecture and how the single Oracle.exe process has to live within 
3Gb on 32bit. Sure 64bit ups that but if we have to move why not consider 
all options not just blindly follow MS?

I'm trying to put together what the real limits in memory are under Unix 
(probably HP-UX as HP are our main supplier) and Linux (RH looks soooo good 
on paper when comapred with MS). I've trawled the relavant home pages and 
got some good info but some tends to be contradictory if not downright 
unclear. Initially we'd use Oracle 9i as I'm not comforatble with 10g yet.

What I would like is some guidance (or pointers to good trustworthy FAQs) on 
how much memory each Oracle process can use - for instance 32bit RH Linux 
says 4Gb per process but does the OS steal any (coz Windows would). Or is 
that really 4Gb per process - so if I had 64Gb in the machine I get 4Gb for 
a number of oracle process should I need them. I am going to get questioned 
on that when I make my proposals and would like hard facts not vendor 
"promises". Also are there any other gotchas I need to know about (and can 
relate plenty in Windows I can assure you). Yes I'm naive when it comes to 
such things on Unix/Linux!

Thanks for even reading this far!


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