Abstract: Embedded real-time database systems not only need higher success-ratio but also often run without human interruption. Real-time transactions must support function alternative so as to have both adjustability and suitability. Proposed in this paper is a concurrency control protocol CCCP based on pre-declaration of resources. An alternative becomes the main body of concurrency control in CCCP. In each transaction, one alternative that is most suitable for the system environment executes conflict-freely. Based on transactions priority CCCP protects ready transactions through compatiability analysis. An algorithm with low spending is also given. An experiment proves that CCCP is in favor of choice-suitable alternative and enhancing system success-ratio. So it is suitable for embedded real-time database systems.