Someone contacted me offlist indicating they were also interested in this topic: sharing a scratch pool in a tape library (aka ATL) between z/VM a nd z/OS, using RMM on z/OS and Tape Manager on z/VM.
So here's a summary of the considerations: 1. Will your VM application (that's writing to tapes) respect the full VO L1 header that z/OS requires? I.e. when a tape previously used by z/VM is scratched, it might be used next by z/OS, so the full VOL1 header needs t o be intact. If your VM application is running in OS-simulation mode, then you're probably ok. If it's not, then you need to dig further and find out. Many CMS applications don't maintain the full VOL1 header. 2. Tape Manager's support for RMM allows you to specify the scratch category you want to use in the ATL - so, although you can, you don't hav e to share the scratch pool with z/OS. However, when tapes expire and move back to scratch, RMM puts them in the z/OS scratch category, no matter where they started. So again, you could have tapes without full VOL1 headers in the z/OS scratch category. 3. You can get around item 2 by either: a. Marking the USE(VM) field for all the tapes you will be using on z/VM. That way if RMM expires them back to the z/OS scratch category, z/OS won' t try to mount them and you can find them and move them back to the z/VM scratch category on some regular interval. Of course, this means you're really maintaining a separate set of tapes for z/VM, and aren't truly "sharing". b. Maintaining a separate tape catalog for your z/VM tapes in Tape Manage r, and assigning separate volser ranges to RMM and Tape Manager. Again, you're not truly "sharing" the tapes - just sharing the ATL. Bottom line - the only way to truly share tapes with z/OS is to make sure your VM application respects the full VOL1 header as z/OS requires. Otherwise, you have to maintain separate volser ranges for each operating system. Keep in mind that none of this discussion relates to the devices in the ATL. You can still dynamically share the devices in the ATL, letting each operating system grab one when it needs one and give it up when it's done . Tape Manager on z/VM and Automated Tape Allocation Manager on z/OS suppor t the device sharing. Not sure how much of a "summary" that is, but there you have it. Tracy Dean IBM
