Fault tolerance assurance methodology of the SXO operating system for continuous operation

In developing the SXO operating system for the SURE SYSTEM 2000 continuous operation system, the authors aimed to create an unprecedentedly high software and hardware fault tolerance. They devised a fault tolerant architecture and various methodologies to ensure fault tolerance. They implemented these techniques systematically throughout operating system development. In the design stage, they developed a design methodology called the recovery process chart to verify that recovery mechanisms were complete. In the manufacturing stage, they applied the concept of critical routes to recovery and other processes essential to high dependability. They also developed a method of finding critical routes in a recovery process chart. In the test stage, they added an artificial software fault injection mechanism to the operating system. It generates various reproducible errors at appropriate times and reduces the number of personnel needed for test, making system reliability evaluation easy