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1 votes
1 votes

Let us assume that transaction $T1$ has arrived before transaction $T2$. Consider the schedule $s=r1(A);r2(B): w2(A);  w1(B)$

Which of the following is true?

  1. Allowed under basic timestamp protocol.
  2. Not allowed under basic timestamp protocols because $T1$ is rolled back.
  3. Not allowed under basic timestamp protocols because $T2$ is rolled back.
  4. None of these
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3 Answers

7 votes
7 votes
  • if a schedule is conflict serializable schedule then it is allowed in basic timestamp protocol but the given schedule is not conflict serializable so it is not allowed in basic timestamp.
  • in basic timestamp ordering protocol, the conflicting operation should be executed in the timestamp order but in given schedule $\mathbf{T_2}$ is violating this. So we need to rollback.
edited by
3 votes
3 votes
According to basic timestamp ordering protocol conflicting operation should be executed in the timestamp order.

Here T2 performing read on B, than its timestamp will be newer and when older transcation perform Write on B i.e T1 than it voilated our condition. so

option B is right ans,
Answer:

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