A class group is an instance of the Data-Admin-DB-ClassGroup class.
A class group instance causes the system to store the instances corresponding to two or more concrete classes that share a common key format in a single database table. The name of the class group is a prefix of the names of the member classes.
Class groups are commonly used to cause the system to store instances of similar or related work item concrete classes together in one relational database table. This is known as a work pool. Work pools are referenced in access group instances.
Class groups correspond to tables in the PegaRULES database, not tables for external classes. Each external class has a corresponding unique database table instance (Data-Admin-DB-Table class) and so cannot be part of a class group.
The Clone a Class Group landing page tab, on the Data Model — Classes and Properties landing page, lets you duplicate the structure of a class group.