A nonunique primary index (NUPI) or a PA (all PAs are nonunique) neither requires nor enforces uniqueness on the index values. Choosing an inappropriate set of index columns for a NUPI or PA may cause a skewed data distribution so careful consideration of the choice of index columns and the table’s map is important.
To enforce uniqueness of the index columns of a NUPI or PA, a separate unique secondary index (USI) can be defined. See Secondary Indexes (Overview) for a discussion of USIs.