A database (DB) server in which a database management system (DBMS) operates and a prefetch server connected to a storage device storing DB data are provided with an acquiring unit for acquiring information on a storage location on the storage device of a DB schema managed by the DBMS, information on DB processing executed by the DBMS, and information on an access to DB data made when the DBMS executes the DB processing, from the DB server, a predictor for predicting data to be read out on the basis of the acquired information, and a prefetch instructing unit for providing the storage device with an instruction to prefetch the corresponding data. Having received the prefetch instruction, the storage device reads out specified data onto a cache memory.