Another Swapissue and Oracle

[arboned_1]

We just got two superdome servers in. And now we are going to size them. The first question how much swapspace do I allocate. The system has 24Gb of memory and we going to run Oracle 9i. Do I really need 24Gb swap. That's al lot of space.

[Stefan Farrelly]

Yes, you need 24Gb. Processes loaded into memory need to reserve swap on disk in case they need to be paged to if you are going to load into memory almost 24Gb of processes then you will have to have 24GB of swap. If you're going to run oracle with say 12Gb of shared memory (this doesnt need to reserve swap) and only load 12Gb of processes into memory then you only need 12Gb of swap. How big are you going to set shared memory/SGA size in your db(s) ?

For crashdump it its quite intelligent now so you dont need to set it to the full 24Gb. Again it depends on what/how much is loaded into RAM. You could probably get away with only 12Gb for dump - but the important issue is how much shared mem/SGA size as per above.

If I had the space though to be safe I would set swap to 24Gb.

[John Palmer]

The answer as always with swap space is... it depends on the workload, specifically the total amount of process data space required.

Provided you configure the kernel with swapmem_on=1 however you'll reduce the requirement for real swap space by about 18Gb, as the kernel will allow up to this amount of data not to have swap space reserved.

I suspect that you don't want processes to do much 'swapping', that's why you've purchased 24Gb! so you could easily get away with as little as say 4Gb of swap space initially. You can easily add more device swap later if it's required.

Regards,
John