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Recoverability (cont)

Recoverable schedules avoid these kinds of problems.

For a schedule to be recoverable, we require additional constraints

  • all tx's Ti that wrote values used by Tj
  • must have committed before Tj commits
and this property must hold for all transactions Tj

Note that recoverability does not prevent "dirty reads".

In order to make schedules recoverable in the presence of dirty reads and aborts, may need to abort multiple transactions.