Ingres constraints, which are defined using the CREATE TABLE and ALTER TABLE statements, must be identical among replicated databases. If the statements are not identical, a Replicator Server transmission error can result. The error occurs when a server is attempting to replicate data into a target database and finds that this violates the constraints of the target database.

In addition, keep in mind that referential integrity constraints cause irresolvable situations if rows related by the constraint are updated on different databases. For example, if a user deletes a customer information row in one database, while another user adds a purchase order for that customer in a second database, and there is a constraint on the purchase order table to the customer table primary key, the purchase order cannot be propagated to the first database. Because this is not a conflict between the same row in the two databases, automatic collision resolution cannot correct this.

The CREATE INTEGRITY statement, which is used to define integrity constraints, must also be identical among replicated databases.