Data writing into a storage device. Data is written into a cache memory in order to implement speeding-up, and also the data is written into a physical disc asynchronously therewith. Since allocation of the cache memory is performed on each writing-request basis, a cut-out processing is required which is executed when none of available areas exists. This results in a problem of necessitating a writing processing time. A DBMS server in advance notifies the storage device that a writing will take place. A manager included in the storage device performs acquisition of the cache memory prior to the writing processing. This allows the data to be stored into the acquired cache memory at the time of the writing processing.