In one general aspect, a computer system can include instructions stored on a non-transitory computer-readable storage medium. The computer system can include a upgrade portion identifier configured to identify a plurality of databases of an original system for upgrade, and a parameter module configured to calculate a plurality of parameter values representing aspects of the plurality of databases. The computer system can also include a fuzzy logic module configured to calculate, using fuzzy logic, a relative ranking of each database from the plurality of databases based on the plurality of parameter values, and a selection module configured to select at least a portion of the plurality of databases for upgrade during uptime of the original system based on a limitation of an upgrade resource and the relative ranking of each database from the plurality of databases.