Distribution networks are approaching the critical point whereby the connection of Distributed Energy Resources (DER) requires taking an active approach. Active distribution management allows the integration of distributed energy resources, storage devices and electric vehicles and open new market opportunities to customers. In the paper a centralized distribution management system is proposed for the optimal operation of active networks. The overall architecture of the system is presented as well as the optimization algorithm. The communication system that is necessary for DMS is also discussed. Some results are presented to show the benefits of the novel paradigm of distribution systems. Finally, the role of the accuracy of estimates is pointed out to show the impact on the effectiveness of DMS.