UGC NET JULY 2018 (Computer Science And Applications Paper-II) (Question 14)

UGC NET JULY 2018 (Computer Science And Applications Paper-II) (Question 14)

Q14. A software system crashed 20 times in the year 2017 and for each crash, it took 2 minutes to restart. Approximately, what was the software availability in that year ?

(1).  96.9924%                                                          (2).  97.9924%
(3).  98.9924%                                                          (4).  99.9924%

Answer : (4).  99.9924%

Reason :  We are given with Mean Time To Repair (MTTR) is a basic measure of the maintainability of repairable items. It represents the average time required to repair a failed component or device.
i.e.  MTTR = 2 mins (2 mins to restart after crash)


Mean time between failures (MTBF) is the predicted elapsed time between inherent failures of a mechanical or electronic system, during normal system operation. MTBF can be calculated as the arithmetic mean (average) time between failures of a system.

MTBF  =               Total Running Time in Year                          =        365 x 24 x 60    
                   Number of Times System Crash in a Year                                  20

MTFB  =  26230

Now we need to find Availability of Software in a Year =              MTBF             =         26230      
                                                                                                  MTBF + MTTR               26230 + 2 
                                                                                        
                                                                                         =  0.9999239  =  0.9999239 x 100 %

                                                                                         =  99.99234 %