Patent US 5,809,503

A locking mechanism for a check-in/check-out model in which one or a plurality of clients make access to a public database of a server, includes a long transaction management part, provided in the server, for managing transactions including a check-out which copies data from the public database and a check-in which writes data back to the public database requested from the client, a short transaction management part, provided in the server, for managing transactions which do not copy data from the public database, and a transaction list storing information indicative of contents of transactions carried out by each of the long transaction management part and the short transaction management part. The long transaction management part waits the check-in of arbitrary data until another transaction making reference to the arbitrary data ends when the other transaction is detected from the transaction list between the check-out and the check-in.