MRP performance concerns with large numbers of materials

I am in the design and build phase for a new SAP implementation. We

will be using time-phased planning with requirements as the MRP type

for all materials, and MRP will run once a week on a sunday night. Each

MRP run will probably involve planning about 50,000 different materials

in each of two plants (total 100,000 plant/materials), and this volume

may well double to 200 000 plant/materials over the next 2-3 years.

We are concerned about the runtime and system resources required for

such a large MRP run. We wont have the production box set up for some time, and we wont be in a position to run any volume testing until shortly before go-live next year - we certainly dont want any nasty surprises then!

I know this is not an exact science, but I would like to know if anyone out there has experience of running MRP and planning a similar (or larger) number of materials. I dont think it matters much if you use a different MRP type, but please bear in mind that net change planning can dramatically reduce the number of materials planned, and I am interested in the number of materials which are actually planned during each MRP run, rather than the number which could potentially be planned.

If you do have such experience, could you share a little information about your system resources, number of materials, and the eventual runtimes you achieved in MRP? This may help me to predict whether we will have a problem at go-live, and to make sure our technical people allow adequate resources when they build our production system

Thanks, Chris