A distributed transaction is a transaction that spans more than one local database. To the Ingres Star user, a distributed transaction looks like a transaction on a single local database. The user issues a single commit or rollback statement to end the distributed transaction. But a distributed transaction may actually involve multiple local transactions. If it does, Ingres Star coordinates these local transactions so that they behave like a single transaction. Therefore, either all of the data in a distributed transaction is committed or none of it is. Ingres Star uses a protocol known as a two-phase commit to ensure that this is what happens.