Transactions and Concurrency

Consider the following classes of schedules: serializable, conflict-serializable, view serializable, recoverable, avoids-cascading-aborts, and strict. For each of the following schedules, state which of the preceding classes it belongs to. If you cannot decide whether a schedule belongs in a certain class based on the listed actions, explain briefly. The actions are listed in the order they are scheduled and prefixed with the transaction name. If a commit or abort is not shown, the schedule is incomplete; assume that abort or commit must follow all the listed actions.

1. T1:W(A), T2:R(B), T1:R(B), T2:R(A) 2. T1:R(A), T2:W(A), T1:W(A), T2:Abort, T1:Commit 3. T1:W(A), T2:R(A), T1:W(A), T2:Abort, T1:Commit 4. T2:R(A), T3:W(A), T3:Commit, T1:W(B), T1:Commit, T2:R(B), T2:W(C), T2:Commit 5. T1:R(A), T2:W(A), T2:Commit, T1:W(A), T1:Commit, T3:R(A), T3:Commit

Question 5 (10 marks) Consider the following classes of schedules: serializable, conflict-serializable, view serializable, re- coverable, avoids-cascading-aborts, and strict. For each of the following schedules, state which of the preceding classes it belongs to. If you cannot decide whether a schedule belongs in a certain class based on the listed actions, explain briefly. The actions are listed in the order they are scheduled and prefixed with the transaction name. If a commit or abort is not shown, the schedule is incomplete; assume that abort or commit must follow all the listed actions. [2 marks each] 1. Tl:W(A), T2:R(B), T1:R(B), T2:R(A) 2. TI:R(A), T2:W(A), Tl:W(A), T2:Abort, T1:Commit 3. T1:W(A), T2:R(A), Tl:W(A), T2:Abort, T1:Commit 4. T2:R(A), T3:W(A), T3:Commit, T1:W(B), T1:Commit, T2:R(B), T2:W(C), T2:Commit 5. T1 R(A), T2:W(A), T2:Commit, T1:W(A), Tl:Commit, T3:R(A), T3:Commit