Talk to the person who liases with IBM and you should be able to discover how charging is calculated, and therefore what could be addressed to reduce charging. "Unused" but "allocated" DASD is a potential. To know what sort of things to prioritise, you need to know the detail of the charging.
After you have got initial information, might be worth finding the person in Accounts who is responsible for monitoring this. You will then also know how the bosses will see the results of any savings you achieve.
Joined: 06 Jun 2008 Posts: 8154 Location: East Dubuque, Illinois, USA
Is the machine purchased, leased, or rented? Is system usage capped -- and is your site running well under the cap, near the cap, or over the cap? Are you looking at hardware costs, or overall costs including software? These are the types of questions that would have to be answered before your questions even make sense -- if the machine was purchased, for example, you could reduce CPU usage to zero and costs for the hardware would not go down one penny since the money was already spent. Depreciation and residual value have to be considered, as well.
The ONLY time you can talk about "average billing rate" for a mainframe would be if you are running your programs at a third-party vendor site that billed computer usage. IBM contracts can vary drastically, so there probably is no such thing as an "average" billing rate.
Hardware costs are only a part of the picture, too. IBM charges monthly fees for everything from the operating system to compilers to utilities. The montly charges may exeed the monthly maintenance fee for the hardware. And the monthly software charges probably won't go down if one application's CPU usage goes down.
Furthermore, you haven't mentioned anything about third-party software costs (from companies such as CA, Compuware, BMC, ASPG, SEA, and so forth), which can be a substantial portion of the overall costs of the mainframe. These contracts can be usage-based, or time-based, or some combination of the two, so these costs may -- or may not -- go down if one application starts using less CPU.
Bottom line: your questions sound reasonable, but they are very complicated to answer since so much depends upon the individual site and its contracts with vendors. The only way to answer your questions would be to consult your site support group. And it is very possible that they don't know since the contract details may not have been provided to them -- if so, only your management could provide you an answer.
As said earlier, it depends upon the agreement, in some cases there might be a flat charge for the CPU used.
No matter if you use too much or don't use at all, there will be a fixed rate charged.
For DASD media charging may be 'usage based' (allocated) or the number of DASD volumes(unallocated as well on the volume).
Edited: Did not see Robert's reply