Abstract: A transfer control method includes a selecting step which selects one of a first route for making an asynchronous transfer to a request destination via a control block and a second route for making a synchronous transfer to the request destination by not passing the control block, with respect to a request from a request source.

Abstract: An I/O interface control method and data processing equipment each of which can avoid data destruction in an I/O unit even when a channel control unit is in a check/stop state. When an abnormal state notification signal from the channel control unit has been received, the channel element completes an I/O operation in execution to halt a transmission to a new I/O operation. When the abnormal state notification signal delayed by a predetermined time has been received, the main storage control unit separates the channel control unit from the channel element to halt the data transmission. The present invention can be applicable to computer systems each including a DASD acting as an I/O unit.