[DBMS] Lost Update and WW

Question

Consider thw following schedules :-

S1 :- W1(A) W2(A) W1(B) W2(B)

S2:- W1(A) R2(A) W2(A) W2(B) W1(B)

Assume that schedule S1 is failed after performing W1(B). Which of the following options are true?

a.) S1 and S2 has lost update problem and WW problem.

b:) S1 and S2 are free from lost update problem and WW problem

c) S1 has WW problem and S2 has lost update problem

d) S1 has lost update problem and s2 has WW problem

Answer 1

S1 has lost update problem and S2 has WW and WR problems. So, d) seems correct.

Comments

I dont have the answer. In s2 even if it is not the blind write,but still update of T1 on A is getting lost by T2 update on A,so why it is not a lost update? Lost update means simply some updated value is lost what i think .?

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for your doubt https://www.youtube.com/watch?v=N7N-TdqNVRc

but I am not sure whether S1 has lost update or not, because S1 is not going to commit the data so its update at the end is going to lost irrespective of any W-W conflict.

@Bikram sir please guide 

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@reena_kandari

Is lost update problem possible in serializable schedule?