Referential integrity in a federated system
In a federated system, the federated database does not enforce referential integrity among data sources.
However, referential integrity constraints at a data source can affect nickname updates. Suppose that you need to insert data that is on the federated server into a nickname. When the federated server sends the insert to the data source, it violates a referential integrity constraint at that data source. The federated server maps the resulting error to a federated error.
Applications are responsible for referential integrity between data sources.