27 votes 27 votes Consider the following schedules involving two transactions. Which one of the following statements is TRUE? $S_1 :r_1(X); r_1(Y); r_2(X); r_2(Y); w_2(Y); w_1(X)$ $S_2 :r_1(X); r_2(X); r_2(Y); w_2(Y); r_1(Y); w_1(X)$ Both $S_1$ and $S_2$ are conflict serializable. $S_1$ is conflict serializable and $S_2$ is not conflict serializable. $S_1$ is not conflict serializable and $S_2$ is conflict serializable. Both $S_1$ and $S_2$ are not conflict serializable. Databases gatecse-2007 databases transaction-and-concurrency normal + – Kathleen asked Sep 21, 2014 Kathleen 9.4k views answer comment Share Follow See all 2 Comments See all 2 2 Comments reply register_user_19 commented Nov 26, 2018 reply Follow Share Also S1: not a view serializable as no blind write present 3 votes 3 votes smsubham commented Mar 10, 2020 reply Follow Share How to check? (to minimize chances of silly error during exams) 1st instruction is read on X from T1, so look for W. We get w2(Y), see if it for same variable and then if its from different transaction. Here its not so ignore and move ahead. w1(X), same transaction so ignore. 2nd instruction is read on Y from T2, so look for W. We get w2(Y), see if it for same variable and then if its from different transaction. Here it is both, so draw a directed edge from T1 -> T2. As there are only 2 transaction and we already have an edge from T1->T2, so no need to check for subsequent instructions. 3rd instruction is read on X from T2, so look for W. We get w2(Y), see if it for same variable and then if its from different transaction. Here it is both, so draw a directed edge from T2 -> T1. As there is a cycle so its not CS. 0 votes 0 votes Please log in or register to add a comment.
–5 votes –5 votes OPTION IS B IS APPROPIATE ONE vijju answered Sep 25, 2016 vijju comment Share Follow See all 0 reply Please log in or register to add a comment.