ANALYSIS OF A COMPUTER SYSTEM WITH HARDWARE REPAIR AND SOFTWARE REPLACEMENT SUBJECT TO CONDITIONAL ARRIVAL TIME OF THE SERVER
The focus of this paper is on reliability and profit analysis of a computer system of two identical units- one is initially operative and other is kept as spare in cold standby. In each unit, hardware (h/w) and software (s/w) fail independently from normal mode. There is a single server who is allowed to take some time at s/w failure with the condition that he has to visit the system immediately at h/w failure. The unit is repaired at h/w failure while replacement of the s/w by new one is done by giving some replacement time when s/w fails to execute the required instructions properly. Server can leave the system only after finishing all jobs available to him. All random variables are statistically independent. The time to failure of h/w and s/w is exponentially distributed while the arrival time of the server, repair time of h/w and replacement time of s/w are arbitrarily distributed with different probability density functions (pdf). By adopting semi-Markov process and regenerative point technique, the expressions for various reliability characteristics are derived to make profit analysis. The behaviour of some important measures of system effectiveness has also been shown graphically for a particular case.