This means the user has to know the track size of the device which will contain the data set. With system-managed storage, users can let the system select the specific unit and volume for the allocation. This means the user does not need to know anything about the physical characteristics of the devices in the installation. Automated DASD Space Management System-managed storage enables users to automatically reclaim space which is allocated to old and unused data sets. Users can have the system remove obsolete data by migrating the data to other DASD, tape, or have the system delete the data.
Users can also release allocated but unused space which is assigned to new and active data sets.
With system-managed storage, users can provide different backup requirements to data residing on the same DASD volume. Thus, all data on a single volume does not have to be treated the same way. Because users in SMS environment do not need to specify the unit and volume which contains their data, it does not matter to them if their data resides on a specific volume or device type. This permits an SMS administrator to easliy replace old devices with new ones. You can also use system-determined block sizes to automatically reblock physical sequential and partitioned data sets that can be reblocked.