Corporate Subject Data Bases (CSDB) are being introduced to reduce data redundancy, maintain the integrity of the data, provide a uniform data access interface, and have data readily available to make business decisions. During the transition phase, there is a need to maintain Legacy Systems (LS), CSDB, and to synchronize between them. Choosing the right granularity for migration of data and functionality is essential to the success of the migration strategy. Technologies being used to support the transition to CSDB include relational systems supporting stored procedures, remote procedures, expert systems, object-oriented approach, reengineering tools, and data transition tools. For our Customer CSDB to be deployed in 1993, cleanup of data occurs during initial load of the CSDB. Nightly updates are needed during the transition phase to account for operations executed through LS. There is a lack of an integrated set of tools to help in the transition phase.