0 votes 0 votes dhingrak asked Jan 23, 2015 dhingrak 2.9k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
Best answer 2 votes 2 votes Ans: A http://en.wikipedia.org/wiki/Thomas_write_rule Keith Kr answered Jan 23, 2015 • selected Jan 26, 2015 by Keith Kr Keith Kr comment Share Follow See all 4 Comments See all 4 4 Comments reply dhingrak commented Jan 23, 2015 reply Follow Share Isn't c also allowed? Older transaction T2 performs a write on A...then younger transaction T1 performs a read on A( no voilation) as Thomas rule is defined only for Write request T1 performs write on B and then T2 performs read on B (no voilation).. 0 votes 0 votes Keith Kr commented Jan 23, 2015 reply Follow Share Thomas write rule is only for writes and can be summarized as ignore outdated writes. It states that, if a more recent transaction has already written the value of an object, then a less recent transaction does not need perform its own write since it will eventually be overwritten by the more recent one. In option c....there is no such situation of two consecutive writes on same data item. 0 votes 0 votes dhingrak commented Jan 23, 2015 reply Follow Share won't both a and c would be true..?can you please explain why c is not true..? 0 votes 0 votes Keith Kr commented Jan 23, 2015 reply Follow Share In a ---> there are consecutive writes by T2 and T1 on the same item, i.e. B In c --->there are consecutive writes by T2 on A and T1 on B. Here though there are consecutive writes but on different data items. Now read my above comment of Thomas rule statement. 0 votes 0 votes Please log in or register to add a comment.