When DFSMShsm determines that a data set is eligible to be physically moved for a class transition, due to either the storage class and/or storage group having been reassigned, then DFSMShsm invokes DFSMSdss to physically move the data set. If DFSMSdss cannot allocate the data set to the newly assigned storage group, then the transition will be failed. If the data set is successfully moved, then the original data set will be deleted. After this data movement, the data set retains all of its existing attributes, including its name, and can be immediately accessed. The catalog is updated to reflect the new location of the data set.