When set name is specified, the attributes of the set are assigned to the subset. The set and subset refer to the same data set and have the same organization, keys, and key data.

Manual subsets inherit the DUPLICATES option from the set.

Automatic subsets also inherit the DUPLICATES option unless NO DUPLICATES is specified for the set; in which case, duplicates are allowed in the subset.

The subset is automatic if a where condition is specified, and manual otherwise. A manual subset declared in this manner must still be maintained by user programs even though the set is automatically updated.

The subset refers to the data set directly; it does not refer to the set in any way. This option merely allows the attributes of the subset to be specified in abbreviated form.