Data Base Management System #1

Computer Science Level pending

Consider the following log sequence of two transactions on a bank account, with initial balance 12000, that transfer 2000 to a mortgage payment and then apply a 5% interest.

  1. T1 start
  2. T1 B old=12000 new=10000
  3. T1 M old=0 new=2000
  4. T1 commit
  5. T2 start
  6. T2 B old=10000 new=10500
  7. T2 commit

Suppose the database system crashes just before log record 7 is written. When the system is restarted, which one statement is true of the recovery procedure?

We must undo log record 6 to set B to 10000 and then redo log records 2 and 3 We need not redo log records 2 and 3 because transaction T1 has committed We can apply redo and undo operations in arbitrary order because they are idempotent. We must redo log record 6 to set B to 10500

Aswad Hariri Mangalaeng by Aswad Hariri Mangalaeng , 26, Indonesia

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1 solution

Once a transaction is committed, no need to redo or undo operations Once a transaction is committed, no need to redo or undo operations Once a transaction is committed, no need to redo or undo operations

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But what about transaction T2 which was not commited?

Hasmik Garyaka - 3 years, 8 months ago

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