Maintaining Referential Integrity in a Distributed System

If a part of a distributed statement fails, for example, due to an integrity constraint violation, the database returns error number ORA-02055. Subsequent statements or procedure calls return error number ORA-02067 until a ROLLBACK or ROLLBACK TO SAVEPOINT is issued.

Design your application to check for any returned error messages that indicate that a portion of the distributed update has failed. If you detect a failure, you should roll back the entire transaction before allowing the application to proceed.

The database does not permit declarative referential integrity constraints to be defined across nodes of a distributed system. In other words, a declarative referential integrity constraint on one table cannot specify a foreign key that references a primary or unique key of a remote table. Nevertheless, you can maintain parent/child table relationships across nodes using triggers.

If you decide to define referential integrity across the nodes of a distributed database using triggers, be aware that network failures can limit the accessibility of not only the parent table, but also the child table. For example, assume that the child table is in the sales database and the parent table is in the hq database. If the network connection between the two databases fails, some DML statements against the child table (those that insert rows into the child table or update a foreign key value in the child table) cannot proceed because the referential integrity triggers must have access to the parent table in the hq database.