PURPOSE: To promote the communication of data groups stored in different data bases DBs by providing a database link section between an application program(AP) and a database(DB) to reduce man-hours for newly generating an AP.

CONSTITUTION: Upon the receipt of a command from an AP 20, a command analysis section 12 of a database link section 10 discriminates whether or not the command is a command registered in advance in a command storage section 11 and when the command is a registered command, a command conversion section 13 converts the command by a predetermined procedure into a command specific to a DB 30 and the command conversion section 13 sends the command to the DB 30. On the other hand, when the command received from the AP is not a command registered in the command storage section 11, a command non-conversion section 14 does not convert the command received from the AP and sends the command to the DB 30.