Database Reference
In-Depth Information
A log file keeps information necessary for recovery from failures. Two log-
based recovery techniques: deferred updates technique and immediate updates
technique.
Shadow paging, which does not utilize logging, is a less common method for
recovery from database failures.
REVIEW QUESTIONS
1. What are the four essential properties of a database transaction? Describe
any one.
2. List the major operations of a transaction.
3. What is domain integrity? State a few domain integrity constraints or rules.
4. Why is concurrent processing of transactions important in a database envi-
ronment? Describe any one type of concurrency problem.
5. Distinguish between a serial schedule and a serializable schedule. Give an
example.
6. What are S-locks and X-locks? Describe their purposes in transaction
processing.
7. How is timestamp-based concurrency control different from lock-based
techniques?
8. What are the major types of database failures? Briefly describe each.
9. What are the two common log-based database recovery protocols? List their
similarities and differences.
10. What are the advantages and disadvantages of shadow paging?
EXERCISES
1. Match the columns:
1. transaction commit A. no rollback of committed transaction
2. trigger B. database and log synchronization
3. concurrent transactions C. used for deadlock prevention
4. serial schedule D. leaves database in consistent state
5. recoverable schedule E. used for deadlock detection
6. wound-wait scheme F. special type of stored procedure
7. wait-for graph G. desired property of database transaction
8. checkpoint H. confirm database updates
9. isolation I. no interleaved operations
10. atomic transaction J. increased system throughput
2. Define lock-based concurrency control. Why does simple locking not
establish serializability? Describe the two-phase locking protocol and show
how this technique ensures serializability.
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