doubt

Question

Q: Assume T2->T1 is one of non-conflict schedule

Suppose

T1 : R1(B),W1(B)

T2 : R2(B)

NOW., R1(B),R2(B),W1(B)

IS there any problem if R2(B) comes in between R1(B) and R2(B) as shown above ?

Answer 1

I believe your question is if there is a problem if R2(B) comes between R1(B) and W1(B). Answer is no there is no problem. Because it is maintaining T2 -> T1. There is no conflict for R1(B) to R2(B) but R2(B) has to be before W1(B) otherwise R2(B) will read different value of B, and then it will no longer be T2 -> T1, which is not good according to the question.

Answer 2

As the R₂(B) and W₁(B) are conflicting pairs so in that case you can't swap them and eventually your current scheduling won't we conflict serializable.

you can explore more about it here

http://www.geeksforgeeks.org/conflict-serializability/