Problems with mixed DIMM sizes in rp5470?

[Greg OBarr]

I have an rp5470 running HP-UX 11.11 and Oracle 10g. Ran for months with no problems with 8Gb RAM - all 512Mb DIMMs. I shut down the server on 10/29 for the fall-back time change (our apps can't handle it). When I shut down, I added 4Gb of RAM, but they were 1Gb DIMMs. So, I had 12Gb - 8Gb were 512Mb DIMMs and 4 were 1Gb DIMMs. Since then, there were multiple problems with Oracle processes seeming to spawn out of control - ended up having to restart the server several times. Last time, I removed the 512Mb DIMMs and replaced with more 1Gb DIMMs for a total of 16 Gb now. This appears to have solved the problem, but I don't know why. Anybody ever seen anything like this before?

[James R. Ferguson]

Hi Greg:

Mixing 1GB and 512MB DIMMs should not have any impact on your application. Something else must have changed -- kernel or Oracle parameters, perhaps? I'd especially suspect either or both of these, since when you moved from 12GB to 16GB memory your problem resolved itself.

Regards!

...JRF...

[Peter Godron]

Greg,
did you have them in the right order ?
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=947350
RAM also works in pairs on thisd server!

[Greg OBarr]

I didn't actually look at the slots in the memory carrier to see that the 512 Mb DIMMs were installed correctly, I initially just added the 1Gb DIMMs to all the empty slots. I still believe that if there was some sort of problem with this, or a memory problem at all, the system would have identified it in POST and probably disabled the memory at least. I did not change any kernel parameters, but maybe it's possible that a parameter setting could have cause different behavior based on the available memory?

[Torsten.]

Also make sure your PDC version is 44.12 (latest). The PDC will handle all the memory related things (refresh rates etc).