Patent ID: 8347142

Claim:
A method for fault tolerant operation and diagnosis of an I/O (Input/Output) adapter, said method comprising: assigning a primary I/O adapter and a redundant I/O adapter of a data processing system to support access to a system resource; thereafter, while a primary I/O adapter of a data processing system is in service in providing access to a system resource and a redundant I/O adapter of the data processing system is not in service in providing access to the system resource and in absence of an actual fault in the primary I/O adapter, issuing a fail over command to remove the primary I/O adapter from service and to place the redundant I/O adapter in service in supporting access to the system resource; in response to the fail over command, reading a state of the primary I/O adapter, transferring the state of the primary I/O adapter to the redundant I/O adapter, and enabling the redundant I/O adapter to assume support for access to the system resource; while the redundant I/O adapter is in service and the primary I/O adapter is not in service in providing access to the system resource, performing diagnostic testing on the primary I/O adapter; in response to the diagnostic testing revealing no fault in the primary I/O adapter, issuing a fail back command to restore the primary I/O adapter to service and to remove the redundant I/O adapter from service in supporting access to the system resource; and in response to the fail back command, reading a state of the redundant I/O adapter, transferring the state of the redundant I/O adapter to the primary I/O adapter, and enabling the primary I/O adapter to assume support for access to the system resource.