1 votes 1 votes Number of serial schedules but not conflict to schedule (S) S: r1(A),r2(A),r3(A),r4(A),w1(B),w2(B),w3(B),w4(B) Databases transaction-and-concurrency + – manisha11 asked Dec 17, 2018 manisha11 857 views answer comment Share Follow See all 2 Comments See all 2 2 Comments reply OneZero commented Dec 17, 2018 reply Follow Share do you mean the no.of serial schedules that are conflict equivalent to the above schedule? If thats your question then i got only 1 serial schedule : T1-T2-T3-T4 0 votes 0 votes flash12 commented Dec 18, 2018 reply Follow Share Please explain it.. 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes Number of serial schedules which are view equivalent to S but not conflict equivalent to schedule S Conflict equivalent Schedule is T1->T2->T3->T4 view equivalent Schedule are 1. first read same 2. final write same 3. w-R dependency on same on same data item T4 should be last bcz it is final write. T1,T2,T3 can be in any order for view equivalent. Here read operation doesn't matter bcz it is on single data item Answer is 3!-1=5 kavya kamish upadhya answered Dec 17, 2018 kavya kamish upadhya comment Share Follow See all 7 Comments See all 7 7 Comments reply MiNiPanda commented Dec 17, 2018 reply Follow Share @kavya kamish upadhya We need to ensure that only $W_4(B)$ comes at the end right? Rest 7 operations can be in any order (maintaining relative order within each transaction). Then we can arrange the 7 operations in 7! ways and since relative order has to be maintained i.e. $R_1(A)$ has to come before $W_1(B)$,$R_2(A)$ has to come before $W_2(B)$ and $R_3(A)$ has to come before $W_3(B)$ so we have to divide it by (2!) thrice. So shouldn't the answer be $\frac{7!}{ 2! \times 2! \times 2!}=630$ ? 1 votes 1 votes manisha11 commented Dec 18, 2018 reply Follow Share @kavya kamish upadhya ME has solved this way, can you explain in some more depth? 0 votes 0 votes Shubhgupta commented Dec 18, 2018 reply Follow Share @MiNiPanda, but in question it is only asking for serial schedule. in that way you are also calculating non serial schedule. Right? @manisha11, Please edit the question. There is nothing mentioned that you are asking for view equivalent. 0 votes 0 votes MiNiPanda commented Dec 18, 2018 reply Follow Share @ShubhguptaThats right..I didn't take care about the "serial" thing.. 0 votes 0 votes G4TE Hunter commented Dec 18, 2018 i edited by G4TE Hunter Dec 18, 2018 reply Follow Share Number of conflict equivalent schedule are w1->w2->w3->w4 in which r1,r2,r3,r4 arranged as 1x3x5x7x1=105 Number of view equivalent schedule are T1->T2->T3->T4 in which r1,r2,r3,r4 arranged as 1x3x5x7x3!=630 (3! for arranging w1->w2->w3->w4 as w4 is final write ) Then No of view equivalent which are not conflict equivalent schedule =630-105=525 Question need correction bcz Serial is subset of Conflict is subset of View 0 votes 0 votes MiNiPanda commented Dec 18, 2018 reply Follow Share @G4TE Hunter I understand your logic of finding conflict equivalent schedules..but what are you getting after 630-105? These are the no. of schedules which are only view equivalent and not conflict equivalent right? And what does the question ask for? 0 votes 0 votes manisha11 commented Dec 18, 2018 reply Follow Share @Shubhgupta the question had this description only. 0 votes 0 votes Please log in or register to add a comment.