A Model of Recoverability in Multilevel Systems

Backward error recovery (that is, resetting an erroneous state of a system to a previous error-free state) is an important general technique for recovery from faults in a system, especially those faults which were not foreseen. However, the provision of backward error recovery can be complex, particularly if the implementation of the system is "multilever" and recovery is to be provided at a number of these levels. This paper discusses two distinct categories of multilevel system, and then examines in detail the issues involved in providing backward error recovery in both types of system.