CHAPTER 10: TRANSACTION MANAGEMENT AND CONCURRENCY
CONTROL
1. Most real-world database transactions are formed by only one database request.
a. True
b. False
2. To ensure consistency of the database, every transaction must begin with the database in an unstable state.
a. True
b. False
3. Although the DBMS is designed to recover a database to a previous consistent state when an interruption
prevents the completion of a required set of transactions, the transactions themselves are defined by the end
user or programmer and must be semantically correct.
a. True
b. False
4. The DBMS guarantees that the semantic meaning of a transaction truly represents the real-world event.
a. True
b. False
5. Atomicity indicates the permanence of the database’s consistent state.
a. True
b. False
6. Serializability means that data used during the execution of a transaction cannot be used by a second
transaction until the first one is completed.
a. True
b. False
7. Incomplete or improper transactions can have a devastating effect on database integrity.
a. True
b. False
Chapter 10: Transaction Management and Concurrency Control
8. The multiuser DBMS must implement controls to ensure serializability and isolation of transactions, in
addition to atomicity and durability, in order to guard the database’s consistency and integrity.
a. True
b. False
9. Durability requires that all portions of the transaction must be treated as a single, logical unit of work in which
all operations are applied and completed to produce a consistent database.
a. True
b. False
10. The phenomenon of uncommitted data occurs when two transactions are executed concurrently and the first
transaction is rolled back after the second transaction has already accessed the uncommitted data—thus
violating the isolation property of transactions.
a. True
b. False
11. The scheduler establishes the order in which the operations within concurrent transactions are executed.
a. True
b. False
12. A scheduler facilitates data isolation to ensure that two transactions do not update the same data element at the
same time.
a. True
b. False
13. In a page-level lock, the DBMS will lock an entire diskpage.
a. True
b. False
14. A lock guarantees the open use of a data item to multiple transactions.
a. True
b. False
Chapter 10: Transaction Management and Concurrency Control
15. A shared lock produces no conflict as long as all the concurrent transactions are read-write only.
a. True
b. False
16. A field-level lock allows concurrent transactions to access the same row, as long as they require the use of
different fields within that row.
a. True
b. False
17. A growing phase in a two-phase lock is when a transaction acquires all the required locks without locking any
data.
a. True
b. False
18. Timestamps must only have the single property of uniqueness.
a. True
b. False
19. Time stamping demands a lot of system resources because many transactions might have to be stopped,
rescheduled, and stamped.
a. True
b. False
20. When using an optimistic approach, during the read phase, a transaction reads the database, executes the
needed computations, and makes the updates to a private copy of the database values.
a. True
b. False
21. An optimistic approach is based on the assumption that the majority of the database operations do not conflict.
a. True
b. False
Chapter 10: Transaction Management and Concurrency Control
22. When using an optimistic approach, during the write phase, the transaction is validated to ensure that the
changes made will not affect the integrity and consistency of the database.
a. True
b. False
23. The serializable isolation level is the least restrictive level defined by the ANSI SQL standard.
a. True
b. False
24. The reason for the different levels of isolation is to increase transaction concurrency.
a. True
b. False
25. The transaction recovery write-ahead-log protocol ensures that transaction logs are always written before any
database data are actually updated.
a. True
b. False
26. The last step in the write-through technique recovery procedure is to identify the last checkpoint in the
transaction log.
a. True
b. False
27. A transaction is a unit of work that must be either entirely completed or aborted.
a. timed b. practical
c. logical d. physical
28. A consistent database state is .
a. one in which all tables have foreign keys
b. one in which all data integrity constraints are satisfied
c. one in which all tables are normalized
d. d. one in which all SQL statements only update one table at a time
Chapter 10: Transaction Management and Concurrency Control
29. requires that all operations of a transaction be completed.
a. Specificity b. Atomicity
c. Durability d. Time stamping
30. means that data used during the execution of a transaction cannot be used by a second transaction until
the first one is completed.
a. Serializability b. Atomicity
c. Isolation d. Time stamping
31. All transactions must display .
a. atomicity, consistency, and durability b. durability and isolation
c. consistency, durability, and isolation d. atomicity, durability, consistency, and isolation
32. A single-user database system automatically ensures of the database, because only one transaction is
executed at a time.
a. serializability and durability b. atomicity and isolation
c. serializability and isolation d. atomicity and serializability
33. The ANSI has defined standards that govern SQL database transactions. Transaction support is provided by
two SQL statements: and ROLLBACK.
a. RETRIEVE b. ASSIGN
c. UPDATE d. COMMIT
34. ANSI defines four events that signal the end of a transaction. Of the following events, which is defined by
ANSI as being equivalent to a COMMIT?
a. Five SQL statements are executed. b. The end of a program is successfully reached.
c. The program is abnormally terminated. d. The database is shut down for maintenance.
35. ANSI defines four events that signal the end of a transaction. Of the following events, which is defined by
ANSI as being equivalent to a ROLLBACK?
a. Five SQL statements are executed. b. The end of a program is successfully reached.
c. The program is abnormally terminated. d. The database is shut down for maintenance.
Chapter 10: Transaction Management and Concurrency Control
36. The implicit beginning of a transaction is .
a. when the database is started b. when a table is accessed for the first time
c. when the first SQL statement is encountered d. when the COMMIT command is issued
37. The information stored in the is used by the DBMS for a recovery requirement triggered by a
ROLLBACK statement, a program’s abnormal termination, or a system failure such as a network discrepancy
or a disk crash.
a. data dictionary b. metadata
c. rollback manager d. transaction log
38. One of the three most common data integrity and consistency problems is .
a. lost updates b. disk failures
c. user errors d. deadlocks
39. occurs when a transaction accesses data before and after one or more other transactions finish working
with such data.
a. Inconsistent retrievals b. The phenomena of uncommitted data
c. Lost update problems d. Dirty read problems
40. As long as two transactions, T1 and T2, access data, there is no conflict, and the order of execution is
irrelevant to the final outcome.
a. shared b. common
c. unrelated d. locked
41. A lock prevents the use of any tables in the database from one transaction while another transaction is
being processed.
a. database-level b. table-level
c. page-level d. row-level
42. are required to prevent another transaction from reading inconsistent data.
a. Locks b. Schedules
c. Stamps d. Logs
Chapter 10: Transaction Management and Concurrency Control
43. The manager is responsible for assigning and policing the locks used by the transactions.
a. transaction b. database
c. lock d. schedule
44. Lock indicates the level of lock use.
a. granularity b. shrinking
c. growing d. serializability
45. A lock locks the entire table preventing access to any row by a transaction while another transaction is
using the table.
a. database-level b. table-level
c. page-level d. row-level
46. A lock locks the entire diskpage.
a. transaction-level b. table-level
c. page-level d. row-level
47. A diskpage, or page, is the equivalent of a .
a. database table b. disk sector
c. database schema d. diskblock
48. A lock allows concurrent transactions to access different rows of the same table.
a. database-level b. table-level
c. page-level d. row-level
49. A(n) lock has only two stages (0 and 1).
a. shared b. exclusive
c. binary d. two-phase
50. A(n) specifically reserves access to the transaction that locked the object.
a. shared lock b. exclusive lock
c. binary lock d. deadlock
Chapter 10: Transaction Management and Concurrency Control
51. A(n) lock exists when concurrent transactions are granted read access on the basis of a common lock.
a. shared b. exclusive
c. binary d. two-phase
52. What is a rule that applies to the two-phase locking protocol?
a. Two transactions cannot have conflicting locks.
b. No unlock operation can precede a lock operation in a different transaction.
c. No data is affected until all locks are released.
d. No data is affected until the transaction is in its locked position.
53. A(n) phase in a two-phase lock is when a transaction releases all locks and cannot obtain any new lock.
a. growing b. shrinking
c. locking d. unlocking
54. A occurs when two or more transactions wait for each other to unlock data.
a. livelock b. database deadlock
c. distributed deadlock d. phantom deadlocks
55. A(n) condition occurs when two or more transactions wait for each other to unlock data.
a. deadlock b. exclusive lock
c. binary lock d. two-phase lock
56. In the wait/die scheme,:
a. the older transaction rolls back the younger transaction and reschedules it.
b. the younger, preempted transaction is rescheduled using the same time stamp.
c. the older transaction waits for the younger one to complete and release its locks.
d. both the younger and older transactions wait indefinitely to be released.
57. The approach to scheduling concurrent transactions assigns a global unique stamp to each transaction.
a. scheduled b. table-locking
c. unique d. timestamping
Chapter 10: Transaction Management and Concurrency Control
58. In the optimistic approach, during the phase, a transaction scans the database, executes the needed
computations, and makes the updates to a private copy of the database values.
a. read b. validation
c. write d. shared
59. In the optimistic approach, during the phase, changes are permanently applied to the database.
a. read b. validation
c. write d. shared
60. The isolation level ensures that queries return consistent results.
a. Read Uncommitted b. Read Committed
c. Serializable d. Repeatable Read
61. A(n) occurs when a transaction executes a query at time t1, and then it runs the same query at time t2,
yielding additional rows that satisfy the query.
a. phantom read b. dirty read
c. uncommitted dependency d. nonrepeatable read
62. Although the DBMS is designed to recover a database to a previous consistent state when an interruption
prevents the completion of a required set of transactions, the transactions themselves are defined by the end
user or programmer and must be correct.
63. If a(n) is issued before the termination of a transaction, the DBMS will restore the database only for that
particular transaction, rather than for all transactions, in order to maintain the durability of the previous
transactions.
64. The objective of control is to ensure the serializability of transactions in a multiuser database
environment.
65. control is important because the simultaneous execution of transactions over a shared database can
create several data integrity and consistency problems.
66. The scheduler’s main job is to create a(n) of a transaction’s operation, in which the interleaved
executions of transactions yield the same results as if the transactions were executed in serial order.
Chapter 10: Transaction Management and Concurrency Control
67. The interleaves the execution of database operations to ensure serializability.
68. To determine the appropriate order of the operations, the scheduler bases its actions on concurrency control
algorithms, such as or time stamping methods.
69. The occurs when two concurrent transactions, T1 and T2, are updating the same data element and one of
the updates is lost.
70. Most multiuser automatically initiate and enforce locking procedures, where all locking information is
managed by the lock manager.
71. can take place at any of the following levels: database, table, page, row, or field.
72. -level locks are less restrictive than database-level locks, but they create traffic jams when many
transactions are waiting to access the same table.
73. As a rule, a(n) must unlock the object after its termination.
74. The rule states that only one transaction at a time can own an exclusive lock on the same object.
75. If T1 has not unlocked data item Y, T2 cannot begin; if T2 has not unlocked data item X, T1 cannot continue.
Consequently, T1 and T2 each wait for the other to unlock the required data item. Such a deadlock is also
known as a(n) _____.
76. Uniqueness ensures that no equal time stamp values can exist, and ensures that time stamp values
always increase.
77. In a heavily used database management system (DBMS), the prevention and detection of constitutes an
important DBMS function.
78. ensure that a disk physical failure will not impair the DBMS’s ability to recover data.
Chapter 10: Transaction Management and Concurrency Control
79. Database transaction restores a database from an inconsistent state to a previously consistent state.
80. What is transaction isolation and why it is important?
81. Explain the transaction log. What is its function?
82. How does a shared/exclusive lock schema increase the lock manager’s overhead?
83. What are the three basic techniques to control deadlocks?
Chapter 10: Transaction Management and Concurrency Control
85. How do transaction recovery procedures use the deferred-write and write-through techniques to recover
transactions?