PURPOSE: To prevent the duplication of the same records by adding the history control information to each record and then adding successively these history control information in accordance with the addition/deletion processes applied to the same records.

CONSTITUTION: A single record consists of a data area part 43 and a history control part 44. The part 44 can register plural history control information (addition/deletion sections and generations where addition/deletion occurred) in order of occurrence. In this respect, a record is produced from the part 43 and a piece of history control information when the data is newly produced. Thus the history control information is added to the existing history control information every time the addition/deletion processes are applied to the same records.