Optimal Data Access
With respect to optimal data access using a primary index, you should consider the following factors.
For example, if rows are generally accessed by a range query, you should consider defining a partitioned primary index on the table or join index that creates a useful set of partitions.
If the table is frequently joined with a specific set of tables, then you should consider defining the primary index on the column set that is typically used as the join condition.
See “Access Demographics” on page 417 for details.