Slowly changing dimension type 4 is used when a group of attributes in a dimension rapidly changes and is split off to a minidimension. This situation is sometimes called a rapidly changing monster dimension. Frequently used attributes in multimillion-row dimension tables are mini-dimension design candidates, even if they don’t frequently change. The type 4 mini-dimension requires its own unique primary key; the primary keys of both the base dimension and mini-dimension are captured in the associated fact tables.