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Here Read_TS(X) = 30 when T1 reads X; Now when T3 goes to write X, it's timestamp is 20. Hence TS(T) = 20

But Read_TS(X) > TS(T) . Both rules don't allow this!
How is b correct?

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2 Answers

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T1(30) T2(10) T3(20) 

Consider basic time stamp ordering :  w1(x) to w3(x) not allowed so rellback .

Thomas time stamp ordering : here w1(x) to w3(x) ignored  so Here no rollback

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@Shalini.

The W(X) by T3 will be ignored/rejected by Thomas' write rule and the schedule is completed.

Remember, if you are not able to proceed ahead only then it can be considered that the schedule is not possible. Here, you completed the schedule using the Thomas' rule. So, no issues.

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