Dynamic adjustment of dependability and efficiency in fault-tolerant software

In this paper we discuss the problem of attaining adynamic compromise between using redundancy to improve software dependabilityand limiting the amount of redundancy so as to avoid unnecessary inefficencie A scheme. called self-configuring optimal programming (SCOP) is developed SCOP attempts to reduce the resource cost of faulttolerant software, both in space and time, by providing designers with a flexible redundancy architecture in which dependability and efficiency call be adjusted dynamically at run lime. A design methodology is proposed to introduce support techniques for such dynamic adjustment. Our scheme also suggests a general control framework into which design diversity, data diversity and multiple copies can be incorporated selectively. A detailed dependability and efficiency evaluation shows that SCOP can achieve the same dependability level as those of other existing schemes, while making more efficient use of available resources.