A data processing system is used which is provided with a computer for executing a program, and a storage unit having a cache memory for storing data transmitted as a result of execution of the program and a disk device for storing data stored in the cache memory. The storage unit responds to an input of a request for storing data transmitted from the program to store the transmitted data in the cache memory. Next, the storage unit responds to an input of a request for flashing transmitted from the program to store, in the disk device, the data stored in the cache memory.