1. A computer system with a plurality of database management systems comprising: a disk storage system that stores a plurality of databases; a module that combines databases, said module disposed in a server connected to said disk storage system; and a network that interconnects said disk storage system and said server, wherein said module that combines databases, responsive to receiving user-requested specifications, controls data transfer bandwidth for reflecting update data from a database in said disk storage system to another database; and wherein said disk storage system performs resource allocations for said bandwidth responsive to control from said module that combines databases.