PowerExchange CDC uses Microsoft SQL Server transactional replication technology to access data in SQL Server distribution databases. For CDC to work, you must enable SQL Server Replication on the system from which change data is captured. Also, verify that each source table in the distribution database has a primary key. If your database has a high volume of change activity, use a distributed server as the host of the distribution database. When the extraction process runs, the Microsoft SQL Server Agent must also be running.