This parameter is only required if you are working with raw devices or if you are using the Parallel Server option. In order to access raw devices, use the dd command. See
Supporting the Raw Device Configuration with BRBACKUP and BRRESTORE.Default value:
"ibs=16k"Required value: Definition of the dd options required for reading from tape.
If you define the default value, the data is read from tape in blocks of 16 Kbyte.