Discussion
Which of the following properties of a transaction are handled by Recovery Manager ?
(i) Atomicity
(ii) Durability
(iii) Isolation
(iv) Consistency
Answer: A
The recovery manager handles (i) and (ii), atomicity and durability.
Atomicity requires that a transaction's effects be all or nothing, so after a failure the recovery manager undoes the changes of transactions that did not commit, using the log. Durability requires that committed changes survive failures, so the recovery manager redoes committed changes that had not reached disk.
Isolation is the job of the concurrency control manager, through locking or timestamps. Consistency is the responsibility of the application programmer who writes the transaction, aided by integrity constraints. So options including (iii) or (iv) are wrong.
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