If you specify BACKUPDEVICECATEGORY(DASD), parallel processing is always performed.
Because the backup of the control data sets to DASD is in parallel mode, all of the resources necessary for the backup are allocated before the control data sets and the journal are reserved. This means that DFSMShsm cannot be perform its other functions until either backup is complete or (if concurrent copy is used) concurrent copy sessions have been established and journal backup is complete.