PURPOSE: To read update records, having an unreported revision number larger than a maximum updated revision number which is reported this time, at the same time, to improve the throughput efficiency, and to speed up the reading operation.

CONSTITUTION: A write process 1 updates the revision number added to a record in a data base 3 when the record is updated, and reads out the maximum revision number which is used after a transaction process and reports it to a process 2. The read process 2 holds the maximum revision number of a recorded which is read already in a storage device 7, and compares the updated maximum revision number with the maximum read revision number in the storage device 7 by a comparator 6 when the updated maximum revision number is reported from the write process 1; only when the former is larger than the latter, records having revision numbers larger than the latter read maximum revision number are retrieved in the data base 3 and read out.