- Five recovery techniques are listed below. For each situation described, decide which of the following recovery techniques is most appropriate.
- Backward recovery
- Forward recovery (from latest checkpoint)
- Forward recovery (using backup copy of database)
- Reprocessing transactions
- Switch
- A phone disconnection occurs while a user is entering a transaction.
- A disk drive fails during regular operations.
- A lightning storm causes a power failure.
- An incorrect amount is entered and posted for a student tuition payment. The error is not discovered for several weeks.
- Data entry clerks have entered transactions for two hours after a full database backup when the database becomes corrupted. It is discovered that the journalizing facility of the database has not been activated since the backup was made.
- What is the advantage of optimistic concurrency control compared with pessimistic concurrency control?
- What is the difference between shared locks and exclusive locks?
- What is the difference between deadlock prevention and deadlock resolution?
- Briefly describe four DBMS facilities that are required for database backup and recovery.
- What is transaction integrity? Why is it important?
- List and describe four common types of database failure.
- [Briefly describe four threats to high data availability and at least one measure that can be taken to counter each of these threats.
- List and briefly explain the ACID properties of a database transaction.
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