The internal key of an instance is the text value of a reserved property @baseclass.pzInsKey. This property is defined in the ultimate base class and so is available in every class. This value is also known as the handle.
For rule instances, the date and time that the rule was first saved is a portion of the internal key. As a result, the pzInsKey property has no value until the new rule instance is saved and committed.
When a database administrator creates a new table in the PegaRULES database, it is important to include a database constraint that identifies the pzInsKey column as the primary key of the table.
Don't confuse the internal key with the visible key. The internal key includes the class name and a creation date and time for the instance; the visible key does not.