Assignment 5: Logging and Recovery
Due beginning of class Friday, 27 April, 2012
(assignments turned in by beginning of class on Wednesday, 25 April will be graded and available for pickup by 30 April.)
exercises
- Textbook exercise 18.4 part 2
- Given Textbook figure 18.9,
and an initial database state where
P1=T0, P2=T0, and P3=T0 (use the transaction that updated the
value as the
value of the data item
after the update). Assume
the fuzzy checkpointing described in class (essentially the same
as describe in the book, although the book is a bit light on
details.)
- How many different possible database states are there at the time we
begin recovery from the crash? Think about what the fuzzy checkpoint
means.
- Show three possible states of the database at the time of the crash.
- For one of your states, describe the recovery process (use either
the undo-redo logging described in class, or the ARIES algorithm from the book.
- In section 18.6.3 (Crashes during Restart), the book says
the use of CLRs ensures that the Undo action for an update log record is not applied twice.
The undo-redo locking protocol we discussed in class did not require CLRs.
Explain why the ARIES recovery algorithm requires CLRs, and undo-redo logging does not.
Turning in the assignment
The safest way to turn in the assignment is through
Blackboard; this ensures that we know when
it is turned in, and protects against loss. However, I realize
that some of this is easier to do by hand rather than electronically,
so handing in hard copy at the beginning of the class is acceptable
as well.
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