An improved duplex system is disclosed having a primary system with a primary database and a redundant system with redundant database. The improvement includes a Change List Table (CLT) that records key information regarding each transaction performed on the primary database, which must also be performed on the redundant database to maintain synchronization between the primary and redundant databases. The key information for an i^th transaction recorded in the CLT is removed from the CLT when the i^th transaction is successfully performed on the redundant database.