Patent ID: 7219191

Claim:
A data sharing method for sharing data between a first host computer and a second host computer, the first host computer having a first disk control device, a first database application and a first database system, the first database system including a first remote execution program, and the second host computer having a second disk control device, a second database application and a second database system, the second database system including a second remote execution program, the method comprising: executing a copy direction invert command to the first disk control device to invert a copy direction of data between the first disk control device and the second disk control device, wherein the first host computer executes the copy direction invert command using the first remote execution program; executing a copy direction invert request to the second disk control device to invert the copy direction in response to the copy direction invert command, wherein the first disk control device executes the copy direction invert request; inverting the copy direction and issuing a complete response to notify the first disk control device that inverting has occurred; issuing a command completion response to notify the first host computer of completion of the copy direction invert command, and upon receipt of the command completion response, closing access to the first database system, such that simultaneous execution of the first database application and the second database application is prevented; issuing a remote execution request to the second host computer in response to the command completion response, wherein the first host computer executes the remote execution request using the first remote execution control program; executing a command to access the second disk control device in response to issuing the remote execution request to the second host computer; determining whether or not the second disk control device is designated as a primary disk control device; and if the second disk control device is designated as a primary disk control device, then accessing the second disk control device, wherein if the second disk control device is not designated as a primary disk control device, then the second disk control device is not accessed.