Let nhìn vào những gì sẽ xảy ra nếu 2 thực hiện mà không có ngoại lệ và kết quả của nó được gửi đến AT, nhưng họ không vượt qua AT. Nếu thời hạn cho kết quả chấp nhận được chưa hết hạn và một DRA mới tùy chọn có sẵn, đầu vào là reexpressed và chính được thực hiện với các dữ liệu đầu vào mới. | 196 Software Fault Tolerance Techniques and Implementation The executive discards the checkpoint and clears the WDT the results are passed outside the RtB and the RtB is exited. Primary s Results Are On Time but Fail Acceptance Test Successful Execution with Re-Expressed Inputs Now let s look at what happens if p executes without exception and its results are sent to the AT but they do not pass the AT. If the deadline for acceptable results has not expired and a new DRA option is available the inputs are reexpressed and the primary is executed with the new input data. Differences between this scenario and the failure-free scenario are in gray type. This scenario is similar to the previous scenario except for the cause of p s initial failure. Upon entry to the RtB the executive performs the following a checkpoint or recovery point is established a call to p is formatted and the WDT is set to WP. p is executed. No exception or time-out occurs during execution of p. The results of p are submitted to the AT. p s results fail the AT. Control returns to the executive. The executive checks to ensure the deadline for acceptable results has not expired it has not in this scenario and checks if there is a nother DRA option available that has not been attempted on this input there is one available . The executive restores the checkpoint then calls the DRA with the original input data as its argument. The executive formats a call to p using the re-expressed input. p is executed. No exception or time-out occurs during execution of p with the re-expressed input. The results of p are submitted to the AT. p s results are on time and pass the AT. Control returns to the executive. The executive discards the checkpoint and clears the WDT the results are passed outside the RtB and the RtB is exited. Team-Fly Data Diverse Software Fault Tolerance Techniques 197 All Data Re-Expression Algorithm Options Are Used Without Success Successful Backup Execution This scenario .
