In a main memory database system constituted of the dual memory architecture of PRAM and DRAM as a main memory, a method for updating data in PRAM and DRAM includes Move-When-Write, memory allocation scheme in the dual memory architecture, and a method for dividing and storing database components in the PRAM and DRAM, comprises: determining properties of database components; determining which the components have higher importance required for maintaining the consistency and integrity in a database according to the determined properties of database components; if importance of some of the database components is determined to high level, transmitting the determined high components to PRAM; storing the transmitted database components in PRAM; if importance of some of the database components is determined to low level, transmitting the determined low components to DRAM; and storing lower importance of database components to DRAM, and capturing as snapshot the stored database components by periods, thereby providing very high-speed response time and high transaction throughput by including a Persistent RAM as a main memory and 64-bit processor.