The entire CORBA communication layer at the synchrotron light source ANKA was efficiently upgraded to the next generation device servers, based on Advanced Control System (ACS). The old system, which was running since 2000, required an upgrade to a new version of commercial CORBA libraries. Instead of purchasing a costly license, a decision was made to upgrade to open source TAO CORBA and ACS. The design of ACS is the next step in the evolution of the idea, which lays behind the old ANKA CS, a vision of a control system with distributed CORBA objects for remotely controllable physical devices. The ACS, developed in cooperation with ESO, extended the old device servers with improved management and debugging capabilities and greatly improved the long time stability of servers on Windows NT machines. Adjustment to the new server interface was smooth and without major changes at the fieldbus and client side of the CS. This was possible due to modular object-oriented architecture at all control system layers and good design of interfaces for devices. The code of complex Java clients stayed practically the same, we only had to change the communication plug of Abeans, our core Java libraries. This has significantly reduced the upgrade time because all end-user Java applications remained visually and functionally unchanged. This is also of great value to the operators because no additional training was required. Interfaces to LonWorks device drivers, which are based on functionality of devices, also remained unchanged. In a system with a large number of various devices we were able to keep the whole LonWorks fieldbus intact, we even used the same configuration database with the same set of installed drivers. The smoothness of the upgrade confirms that our developments were focused into the right direction. Now even those users are 100% satisfied with the control system, who always had something to complain about.