Attempting to delete a feature results in the following error.
The features could not be deleted.
Failed to delete relationships for object [ARCFM.Service]
Underlying DBMS error [ORA:01779: cannot modify a column which maps to
a non key-preserved table]
The field is not nullable
ESRI does not permit a relationship class that includes an Oracle/SQL View consisting of more than one table. ArcGIS Desktop 10.1 and older versions did not prevent such a relationship from being created. But the result is a delete relationships error attempting to delete a feature instance. In this example, an editor attempted to delete a Service feature class. The Service feature class has a relationship to an Oracle View consisting of multiple tables.
The relationship in question needs to be removed and an ESRI-supported relationship class created as needed. For more information, please contact ESRI Support.