3: Recovery

Question 1

What is recovery and what is it used for ?

Answer 1

Used in an event of failure that may leave the DB in an inconsistent state.

Question 2

When may a failure occur?

Answer 2

At any point, including the period when data held in buffers is being written to disk for permanent storage.

Question 3

How is a transaction log used ?

Answer 3

The recovery manager establishes the status of any update operations performed by a transaction that may be affected by failure in the system.

Question 4

Name the two types of recovery technique ?

Answer 4

• Deferred Recovery

- Immediate Recovery

Question 5

Which technique favours applying updates to the database (i.e. ‘to disk’, ‘to secondary storage’) when the write operation is performed?

Answer 5

Immediate Recovery

Question 6

Which technique employs ‘force-writing’ of the log to disk in order to preserve the Before-Image (i.e. the old values of the database)?

Answer 6

Immediate Recovery