Oracle Instance - Performance

Question

All -
There are two instances of oracle - both running on 9.2.0.5 on Unix server. Processes on instance A is much faster than the same processes on instance B. Could it be because of some instance level settings on instance B that makes it perform slower than instance A?
Unix Server Configuration:
Sun Fire E2900 with 12 CPU UltraSparc IV+ (1800MHz) and 48GB Memory
Let me know what details should I be looking at?
Thanks

Answer 1

I presume you mean that you have two instances of Oracle 9.2.0.5 on the same Sun UNIX server, rather than on two separate servers. Are they on the same Oracle software installation? i.e. same ORACLE_HOME setting? If so - the hardware and software are all the same thing - then the only differences can be things like:
- Disks and layout over them. Are some disks faster than others?
- Network. Do all users and clients connect in the same for both databases.
- Initialisation Parameters. Assuming you are using a SPFILE, do a
create pfile='/tmp/initA.ora' from spfile ;for both A and B and compare all their settings. Beware of other memory settings if you are using automatically managed memory via SGA_TARGET.
- Database itself - the data in it and indexes on it.
- Application and the SQL it is issuing.
- One instance is simply busier than the other i.e. runs more SQL statements and has more connections to it.
As suggested, running STATSPACK on each database will both help with the workload size each instance is running and identifying any potential bottlenecks. You could also look at the system utilisation using something like 'sar' or 'vmstat', or on Solaris 'prstat' too for finding the most active processes in real time.
Do you have any special system configuration in any way? Or is it just one single system, with everything shared? I'm thinking of Solaris things like Domains, or Zones, or Resource Manager.
John