DB2 10.5 for Linux, UNIX, and Windows

NOT ENFORCED primary key and unique constraints support is added

In DB2® Version 10.5, support is added for NOT ENFORCED primary key and unique constraints. These informational constraints help the query optimizer to select optimal data access plans when index access to the data provides no additional benefit.

If you know that the data conforms to these constraints, you can use the NOT ENFORCED capability to help achieve two goals:

Improve performance, primarily in insert, update, and delete operations on the table
Reduce space requirements that are associated with enforcing a primary key or unique constraint