1. A computer system including instructions stored on a non-transitory computer-readable storage medium, the computer system comprising: a program database module configured to define, at a shadow system, 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; a customization upgrade module configured to select the data of the shadow program database based on a data customization implemented in the original program database of the original system, and configured to define an upgraded program state of the shadow program database based on a combination of the structure of the shadow program database and the data of the shadow program database; a database comparator configured to identify a first portion of an original user database of the original system for upgrade, and configured to identify a second portion of the original user database of the original system for aliasing in the shadow system; and a user database module configured to define, at the shadow system, a shadow user database having a structure defining an upgrade to a structure of the first portion of the original user database.