We currently use IBM's java Hardware Mgmt. Console API to add/remove capacity. It supports the passing of a model # that you want the CPC to be at. This only requires that we have one IBM order # for each CPC.
With HISRV, there is no option to pass a model # so if (for example) you want to change the CPC from a model 704 to a model 705, you would need a specific order# for that. Basically, you would need to create and maintain an order # for every conceivable model that is supported by the CPC.
This would require a mapping of each order # to the model that you desire. We are in the early stages of testing HISRV interface and noticed this difference. We would like to migrate all of our HMC actions to HISRV so we can get out of the business of supporting custom java code.