1. A data transfer control device for synchronizing inputs to a first and a second database having different field definitions and outputs to an application process running on a user terminal, comprising: a session management device issuing a session key identifying said application process; a value transfer destination management device specifying said first database as the transfer destination of data input into a data field in said second database common to the first and second databases and outputting the transfer destination to said application process together with said session key; a database management device inputting the data in the common data field received from said application process together with said session key and updating said first database; and a data request processing device retrieving and outputting the data requested by said application process from said updated first database.