transaction

Question

Comments

Is answer 4! * 2! * 3?

First four instructions can be swapped. 4th and 5th can be swapped. w2(a) can occupy 3 positions if we group last 3. Am not sure if this approach is correct.

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i think it must be 8

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i dont think so, i got 4 only

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@anu

Please explain.

Answer 1

Answer is – 60

let’s fix the W2(A) now to preserve the read write conflict R4,R2,R3(A) should come before it does not matter in which order so total total number of combination will be 3! but we have also W1(B) here which can come before or after W2(A) it does not matter.

so number of cases W1(B) can be put before or after are

lets put W1(B) AND R3(B) before W2(A)  along with R4,R2,R3(A) combinations will be 30

lets put W1(B) along with R4,R2,R3(A) before W2(A) AND R3(B)  after it combinations will be 4! = 24

now put W1(B) AND R3(B) after W2(A) then combination will be W2(A) ,W1(B),R3(B),W2(B) and R4,R2,R3(A) should come before W2(A) does not matter in which order so total total number of combination will be 3! = 6

HENCE number of schedule possible till now is 60