A computer system includes a shadow system including a shadow program database having a structure defining an upgrade to a structure of an original program database on an original system, and having data defining an upgrade to data of the original program database on the original system. The computer system includes a database replicator configured to perform at least one transfer of data from a portion of the original user database into the structure of the shadow user database during an uptime of the original system and configured to perform a final transfer of data from the portion of the original user database into the structure of the shadow user database during a downtime of the original system, and an upgrade transfer module configured to replace the portion of the original user database with the shadow user database after the final transfer of data has been performed.