When you allocate a new data set you can make specific requests for the amount of storage for the data set. You need to specify space attributes for a new data set only if you do not want to use the system defaults.

You can specify a BLOCK of storage in terms of bytes followed by the SPACE operand. SPACE represents the number of primary blocks initially allocated followed by the number of secondary blocks allocated if the primary quantity is not sufficient.

ALLOCATE DATASET(new.data) NEW DIR(4) BLOCK(800) SPACE(20,10) …