Test databases have to be in a known state to provide quality results. Issues during testing can cause the data to become corrupted or out of synch. In addition, the databases can become partially updated or migrated. C2 TDM allows you to bookmark RDS databases at various points in time so you can use a known state (end of month, quarter, year etc) to perform your testing. Once you complete your tests you can simply roll back to that known state and repeat your tests as many times as you need.