[Deploying Sakai] Performance optimisation with Oracle

[Remi Saias]

Hello,

We are running some load testing on one of our future Sakai 2.6.1 
production server and our DBA noticed a problem he described as 
"contention with frequent inserts and updates on 2 tables: sakai_session 
and sakai_presence which causes a lot of "CPU + Wait for CPU" wait events".

 From my point of view I see that our current performance is at least 2 
times slower than what we achieved on our previous pilot instance which 
was running with mySQL and even more annoying is that the performance 
(in transaction per second) is quickly decreasing when I raise the 
number of simulated students in my tests (using The Grinder).

We are using Oracle 10g in a RAC architecture. Anybody have encountered 
such problems or have any clue to how we could improve this situation?

I can provide a lot more details if required! :-)

Thanks in advance!
Remi Saias for the Sakai/OpenSyllabus team at HEC Montreal