The KEK Central Computer System (KEKCC) is a service, which provides large-scale computer resources, Grid and Cloud computing, as well as common IT services. The KEKCC is entirely replaced every four or five years according to Japanese government procurement policy for the computer system. Current KEKCC has been in operation since September 2016 and decommissioning will start in early 2020.
In this talk, we would like to share our experiences and challenges for the security, operation, and some applications dedicated to each experiment. In particular, we report several improvements on the Grid computing system for the Belle II experiment based on the nearly three years operational performance of the KEKCC. We also introduce a prospect for the next KEKCC which is planned to be launched in September 2020.