DATABASE SYSTEM

PROBLEM TO BE SOLVED: To provide a database system capable of minimizing a service stop time accompanying switching when switching a database.SOLUTION: The database system comprises: a memory database 103 for holding data reflecting data update processing requested by an application part 101; and an update log management part 104 for managing log data of data update processing for the memory database 103 and reflecting the log data in a disk database 106 at any time. The update log management part 104 manages log data while dividing them into log data of processing requiring to hold a processing order and log data of processing not requiring to hold the order, and enables the data update processing from the application part 101 to be directly reflected in a disk database 106 after reflecting all the log data of the processing requiring to hold the processing order in the disk database 106, when the memory database 103 becomes unavailable.