The DFSMSrmm scratch pool function in VLPOOL definitions is not honored for scratch mount requests on automated system-managed library resident drives, even if the storage group assigned matches a VLPOOL name. In an automated system-managed library, DFSMS and the library manager control the pooling of scratch volumes with one pool for each media type. There is currently no method to direct mount processing to select a subset of the volumes in a scratch category.

For scratch mount requests on manual system-managed library resident drives, you can decide to implement scratch pools based on storage group names or on any other pooling method provided by DFSMSrmm. When you are pooling based on the storage group name assigned by your ACS routine, any mounted volume must be from that storage group; either in a VLPOOL associated with a tape storage group or the volume has the requested storage group name. When you are pooling using any other method provided by DFSMSrmm, the storage group names are ignored for validation. DFSMSrmm records the storage group name assigned by the SMS ACS routine and ignores any existing storage group name for that volume.

When system managed volumes are moved from being system-managed to non-system-managed, be sure to clear the storage group name unless you plan to continue using storage group pooling. For non-system-managed scratch mount requests that do not request a volume by storage group, DFSMSrmm rejects any volume that already has a storage group name.