Reblocking is the process of changing the number of records in a physical block. The purpose of reblocking is to use the space on the DASD volume more efficiently. DFSMShsm can reblock physical sequential data sets during recall and recovery to any DFSMShsm-supported DASD. If DFSMSdss is the data mover, DFSMShsm can reblock partitioned data sets. When recalling or recovering a data set, DFSMShsm does not determine a blocksize for the data set if the data set VTOC entry indicates that the data set is reblockable. Instead, the blocksize is determined by the DFSMS DASD calculation services.