Node, computer software and method for identifying a target set of entities associated with a first configuration of a computer system that are to be modified for arriving at a second configuration of the computer system. The method includes selecting a single service, determining a characteristic of the single service, wherein the characteristic of the service is indicative of whether the single service is provided in both the first and second configurations, only in the first configuration or only in the second configuration, identifying, based on the selected service and its characteristic, one or two corresponding entity groups that are related to the single service, and mapping subsets of entities associated with the identified corresponding entity groups for transitioning the computer system from the first configuration to the second configuration.