Understanding external classes

For improved application development, understand how your application uses classes that correspond to tables in an external relational database, rather than to a table or view in the PegaRULES database. By reusing external classes, you can include resources from outside the Pega Platform database in your application.

No inheritance or rule resolution applies to external classes, even if the class name contains a hyphen. Because each external class has an associated database table Data-Admin-DB-Table instance, it cannot be part of a class group.

The following methods can operate on an instance of an external class:

• Obj-Browse
• Obj-Open
• Obj-Open-by-Handle
• Obj-Delete
• Obj-Refresh-and-Lock
• Obj-Save
• Obj-Save-Cancel
• Commit
• Rollback

You cannot create Declare Index rules that have an external class as the Applies To key part. However, Rule-Declare-Expressions rules, Rule-Obj-Validate rules, and Rule-Declare-Trigger rules operate on clipboard property values for external classes.

External classes do not contain the @baseclass.pzInsKey and @baseclass.pxObjClass properties, which are present in every internal class. In some cases, no single property in the external class can serve as a unique handle. To support the Obj-Open-by-Handle method with external classes, Pega Platform assembles a substitute string from the key columns of the table.

In certain cases, you can improve the performance of database insert, delete, and update operations for external classes through the optional batchUpdates setting in the prconfig.xml file or dynamic system settings.

System messages sometimes refer to external classes as "Obj-External"; however, Pega Platform does not have an Obj-External method.