Explanation: OPTIMUMDASDBLOCKING | NOOPTIMUMDASDBLOCKING are mutually exclusive, optional parameters indicating whether DFSMShsm should use its defined optimum block size when outputting or recovering to DFSMShsm-owned DASD. Optimum blocking refers to DFSMShsm writing its output or input in blocks that are multiples of 2 KB and is determined by the device’s track size for data being written to DFSMShsm-owned DASD. For example, all models of 3390 DASD have the same track length and an optimum block size of 18 KB (1 KB equals 1024 bytes). This permits better use of space on DFSMShsm-owned DASD devices.
OPTIMUMDASDBLOCKING indicates to DFSMShsm to use its defined optimum block size when writing to DFSMShsm-owned DASD.
NOOPTIMUMDASDBLOCKING indicates to DFSMShsm to not use its defined optimum block size when writing to DFSMShsm-owned DASD. DFSMShsm writes to DFSMShsm-owned DASD in 2 KB blocks.
SMS relationship: Parameter has the same meaning when applied to SMS-managed or non-SMS-managed DASD volumes or data sets.
SETSYS default: None.