Device number allocation for FICON storage groups
When you create a request for a dedicated or shared FICON® storage group, you have the option of assigning device numbers to the requested volumes. If you do not assign device numbers, DPM automatically assigns them when the storage group is attached to a partition.
At that time, DPM looks for device numbers that are already in use by existing partitions, if any, and avoids assigning any conflicting numbers.