These notes describe the various topics and concepts which may be included on the Final Exam. There are also some notes emphasizing topics that will *not* be included on the Final. Below, EC indicates an extra credit topic.

Chapter 6. Locking

• Given a sequence in the form shown on page 197, tell whether it is serializable or not and describe how you determined this.


• Given a lock table, explain whether it's legal or not, i.e., could it ever have the entries shown. (Easy question)


• EC: Discuss some aspects of granular locking, e.g., intention locks.


• Know the three degrees of isolation (Fig. 6.10), how they work and what they imply.

Chapter 8. Database System Recovery

• Discuss the use of checkpoints (if any) in transaction failure versus system failure versus media failure.


• Be able to discuss the example on page 244 and why it is avoided by using strict locking (all locks held until after the commit/abort action is taken).


• Be able to list and describe the four fields in the cache descriptor table in Fig. 8.2 and what they are used for.


• Given some or all of the five operations at the bottom of page 246, be able describe which part of the system is allowed to call them and what each call is used for, what its function is.


• Understand that the address of the page in a log update record is there because of the simplifying assumption of a page-based log and what replaces it when finer granularity is used.


• Give an example of the type of problem that can arise if write-ahead logging is not enforced.


• Describe how force-at-commit can still allow recovery even if some updated pages are not flushed to the stable database. (redo required)


• EC: Describe how the dependent log page address, Fig. 8.8 and related discussion, prevents cache pages from being flushed before the corresponding log records are written.


• Explain the initialization and updating of the list of committed and aborted transactions and the list of active transactions during restart, using a checkpoint.


• Note: Operation logging, starting on pg. 258, will not be on the Final.



Chapter 9. Two-Phase Commit

• Describe what type of errors can arise if a participant were to unilaterally abort or commit during its uncertainty period. (And you have to know where in the sequence of messages and locks the uncertainty period occurs.)


• Thoroughly understand all the failure handling examples in Sec. 9.3, which covers the basic, unoptimized two-phase commit protocol.


• If you are given either Fig. 9.5 or 9.6 on the test, be able to describe what is going on and why the decisions that are made result in a correct commit or abort using the presumed abort protocol.


• In a similar way, be able to discuss the transfer of coordination diagram in Fig. 9.7.



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