Recovery: Searching and Monitoring of Correct Software States

Abstract

The last of the three GAFT processes is called recovery and recovery monitoring. After the detection of an error and possible reconfiguration, the last step is recovering the software, which means that the effect of the error on the software must be eliminated. In line with the previous chapters and [1,2,3,4,5,6], the recovery consists of restoring the last recovery point and continuing the processing. But is this really sufficient? What if latent faults exist in the system and manifest themselves in the system but trigger some detection schemes an arbitrary time later? Assuming this reasonable and unpleasant sequence of events, it becomes clear that just restoring data and program from the last stored recovery point is not enough. We have to admit that we do not have any guarantee that fault is now eliminated: even when hardware is restored or even reconfigured—we have erroneous states of software recorded in recovery points. Thus, we have to consider the recovery process itself and analyze which classic algorithms are applicable and fit the purpose of efficient recovery. We introduce and analyze three recovery algorithms that are able to ensure successful recovery by iteratively go through all stored recovery points.