The Importance of Maintenance Planning - A Case Study

Maintenance planning highly complex, high availability systems is not trivial. In this paper, a case study is presented showing the importance of maintenance planning. The trigger of this study was a system failure that occurred unexpectedly during the test stage caused by a maintenance activity, which was supposed to bring the degraded but still operational network back to a fully-operational state. The system survived the occurrences of multiple link failures; however, it did not survive the corrective maintenance activity. This incident highlights the importance of maintenance planning. Fault-tolerant systems not only have to tolerate the occurrences of faults, but also need to survive the maintenance activities. The causes of the failure are identified and a general scheme to resolve the problem is given.