Question

Q1 20pts Below is a log of a transactional database. LOG <Start T1> <T1, A, 5> <T1, B, 9> <Start T3> <Start T2> <T2, C, 4> <Commit T1> <Abort T2> <Start T4> <T4, B, 9> <Commit T4> <T3, A, 2> crash a. Suppose this was an UNDO-log. What are the values of A, B, and C after recovery? Write \"NA\" if that value is unknowable from this log. b. Suppose this was a REDO-log. What are the values of A, B, and C after recovery? Write \"NA\" if that value is unknowable from this log.

          Q1 20pts Below is a log of a transactional database.
LOG
<Start T1>
<T1, A, 5>
<T1, B, 9>
<Start T3>
<Start T2>
<T2, C, 4>
<Commit T1>
<Abort T2>
<Start T4>
<T4, B, 9>
<Commit T4>
<T3, A, 2>
crash
a. Suppose this was an UNDO-log. What are the values of A, B, and C after recovery? Write \"NA\" if that value is unknowable from this log.
b. Suppose this was a REDO-log. What are the values of A, B, and C after recovery? Write \"NA\" if that value is unknowable from this log.

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Q1 20pts Below is a log of a transactional database.
LOG
<Start T1>
<T1, A, 5>
<T1, B, 9>
<Start T3>
<Start T2>
<T2, C, 4>
<Commit T1>
<Abort T2>
<Start T4>
<T4, B, 9>
<Commit T4>
<T3, A, 2>
crash
a. Suppose this was an UNDO-log. What are the values of A, B, and C after recovery? Write N̈Aïf that value is unknowable from this log.
b. Suppose this was a REDO-log. What are the values of A, B, and C after recovery? Write N̈Aïf that value is unknowable from this log.

Added by Jared G.

Computer Science and Information Technology

Trishna Knowledge Systems 2018 Edition

Instant Answer

Solved by Expert Willis James

Step 1

If this was an UNDO-log, we need to undo the transactions that were not committed before the crash. Show more…

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Q1 20pts Below is a log of a transactional database LOG <Start T1> <T1A,5> <T1,B,9> <Start T3> <Start T2> <T2,C,4> <Commit T1> <Abort T2> <Start T4> <T4,B,9> <Commit T4> <T3,A,2> crash a. Suppose this was an UNDO-log. What are the values of A, B, and C after recovery? Write "NA" if that value is unknowable from this log. b. Suppose this was a REDO-log. What are the values of A, B, and C after recovery? Write "NA" if that value is unknowable from this log.

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