1. A system for controlling resources comprising: a control pattern generation unit that generates a plurality of control patterns from a virtual system model, produced by modeling the behaviors of a network element(s) and a server(s) of a virtual system(s) operating on a virtual datacenter(s), and from a resource allocation change policy stipulating a policy or policies of change of allocation of resources to the virtual system(s); the control patterns proving candidates for control commands to network resources and server resources of the virtual system(s); and a control unit that carries out prediction of a service level, with the use of the control patterns, selecting, with the use of the result of prediction, such control pattern that satisfies the service level of the virtual system(s) and that also satisfies a preset standard or reference for selection, from among the plurality of control patterns, and putting the control pattern selected to use.