When specified as part of an ADD PARTITION clause, the IN area-
    spec inserts a new partition in the index. If you do not specify
    a WITH LIMIT OF clause or OTHERWISE clause, the IN area-spec
    clause creates a new final partition.

    When specified as part of an index STORE clause, the IN area-spec
    clause associates the index directly with a single storage area,
    and all entries in the index are stored in the area you specify.