On-Change Publishing of Database Resident Control System Data

The CERN accelerator control system is largely data driven, based on a distributed Oracle® database architecture. Many application programs depend on the latest values of key pieces of information such as beam mode and accelerator mode. Rather than taking the non-scalable approach of polling the database for the latest values, the CERN control system addresses this requirement by making use of the Oracle Advanced Queuing – an implementation based on JMS (Java Message Service) – to publish data changes throughout the control system via the CERN Controls Middleware (CMW). This paper describes the architecture of the system, the implementation choices and the experience so far.