By notice to extension software technology and modern applications, software reliability and availability is very serious problem. Software fault tolerance techniques improve these capabilities. One of the techniques is Software rejuvenation, which counteracts software aging. Software aging may lead to performance degradation or crash/hang failure or both. Increasing use of software, rapid and unavoidable changes in the operational environment bring many problems for software engineers. One of these problems is the aging and degradation of software performance. Software rejuvenation is a proactive and preventive approach to counteract software aging. By performing calculations and solving equations, we easily calculate the availability of the system for each of the models. In this paper, we address this technique for the application with one, two and three software versions, then extend model for n versions. The numerical experiment results show that with more software versions can greatly reduce expected downtime and improve availability of application. تفاصيل المقالة

In this paper, we focus on the availability of software systems. Software systems with long-running execution may lead to software aging. This phenomenon affects the performance of software system and may eventually cause them to crash or failures. To counteract the phenomenon aging, software rejuvenation is implemented to prevent severe software failures. Generally, when software is initiated, amounts of memory are allocated. Then the body of software is executed for providing a service and when the software is terminated, the allocated memory is released. We propose a software rejuvenation model based on degraded physical memory. This model is implemented with a Markov chain and the system performance due to memory usage, by services, divided into four equal level. Hence, we offer four types of policies for software rejuvenation. The goal of the proposed method is to optimize availability of system. The results we achieve show the superiority of proposed method. تفاصيل المقالة

AbstractToday , almost everyone in the world is directly or indirectly affected by computer systems. Therefore, there is great need for looking at availability in computer systems. Availability is mandatory requirement for many applications. Since the software availability declines with the execution time, also, software aging is a relevant issue in this field. Software aging is a cumulative process that leads long-running systems to age or fail. Software rejuvenation is used to prevent software aging problems. Software rejuvenation measures include rebooting the system or restarting the software to bring the software to a new stable state or empty the memory . In this paper, we intend to use a combination of time-based and measurement-based rejuvenation. Finally , with a numerical example, we compare the combined rejuvenation method with time-based and measurement- based rejuvenation, the results we achieve show this mechanism ensures software availability. Keywords : Software Rejuvenation, Aging, Availability تفاصيل المقالة