adding memory to rx4640 - oracle performance issues

[Rick Garland]

Hi all:

We added memory to an HPUX 11.23 rx4640 system, from 32GB to 64GB and now we are seeing some performance issues within oracle.

Any kernel parms needing to be changed? Any parms in general need to be changed? My thought is that the Oracle SGA needs to be modified but what about on the OS itself?

Thanks all!

[Steven E. Protter · Accepted solution]

Shalom Rick,

Adding memory to a system normally does not provoke performance issues but:

shmmax may need to be increased. This will open up more shared memory for Oracle to use.

swap may need to be expanded. Oracle now has more memory to use, but it needs to reserve swap space and there may not be enough.

http://www.hpux.ws/?p=6
This script will enable you to collect some additional data.

I would gather some Oracle performance data before modifying the SGA. I would also use cstm/mstm or xstm to test the new memory is working right.

SEP

[Rick Garland]

Hi SEP:

Many thanks! Kind of what I was thinking as well. I have been collecting these stats for some time and I am not seeing much difference in the stats from before or after memory install. The parm I would be most interested in (from an OS view) would be the shmmax as it is currently set to 34GB dynamic and is currently using 49%.

Again, many thanks!

[Bill Hassell]

When you add RAM, nothing happens except for (unusual) programs that keep asking for more RAM. Oracle will not do that. Instead, the DBA will increase the SGA to allow for more cached space for temp areas and row storage, etc. But Oracle can be configured to use less memory too. Is it "Oracle" that is running slower (based on stats from the DBA) or is it the application using Oracle. Has RAM usage actually increased with the additional RAM? Which programs actually grew in size? Is performance compute-bound or is disk I/O slowing things down?

[Rick Garland]

Many thanks to Bill and SEP. New manager and she is non-technical and doesn't trust us. Here we go again!