Abstract: Realization of main-memory storage manager (CS21) with data access control through service mediation is introduced. A service that is predicted possible to be executed within the time constraint will be accepted, otherwise it is rejected. The database service mediator (DSM) is an operation prediction model exploiting exponential averaging. The memory manager and indexing in CS21 are also presented briefly. The system has been implemented in a mobile telecommunication system where frequent and fast database access is required. Experimental results show, by blocking some of the database access requests using DSM, the overall real-time characteristics of the system is improved.