First operational experience with the CMS run control system

The Run Control Systemof the Compact Muon Solenoid(CMS) experiment at CERN's new Large Hadron Collider(LHC) controls the sub-detector and central data acquisition systems and the high-level trigger farm of the experiment. It manages around 10,000 applications that control custom hardware or handle the event building and the high-level trigger processing. The CMS Run Control Systemis a distributed Java system running on a set of Apache Tomcat servlet containers. Users interact with the system through a web browser. The paper presents the architecture of the CMS Run Control Systemand deals with operational aspects during the first phase of operation with collidingbeams. In particular it focuses on performance, stability, integration with the CMS Detector Control System, integration with LHC status information and tools to guide the shifter.