DEVICE AND METHOD FOR SWITCHING SYSTEMS IN DUPLEXED SYSTEM

PURPOSE:To prevent a user from sensing switching to a stand-by system while holding a link with a data transmission side computer without disconnecting it even when a fault is generated in a data reception side computer by receiving a message from a terminal by a current system and the stand-by system. CONSTITUTION:Line control terminals 34, 54 respectively include message receiving queues and transmitting queues and successively connect messages received from terminals 6 to 9 and messages to be transmitted to the terminals 6 to 9 to respective queues. In the case of receiving messages from the terminals 6 to 9, a line switching device 5 connects a line to both of the current system 30 and the stand-by system 50 so that both the systems 30, 50 can simultaneously receive the same message. In the case of transmitting messages to the terminals 6 to 9, the device 5 switches and connects the line to the current system 30 so that a message can be transmitted only from the current system 30. Disk devices 3, 4 and shared memories 10, 20 are duplexed.