Abstract: Method and apparatus for efficient upgrading of a software system by a plurality of versions. The invention allows upgrades from an arbitrary software system version to another arbitrary subsequently released software system version at reduced cost and down time by executing an upgrade framework including all upgrade tasks identical for individual upgrade steps between two subsequent software system versions and a plurality of upgrade contents including tasks specific for each upgrade step. The invention allows to upgrade a software system in a real-time environment using a source system operating with an old software version and a target system for operating with the new software version and allows to handle static as well as dynamic data.