Managing Multiuser Databases Questions and Answers

Q: A Transaction Manager is which of the following ?

A transaction manager does all three, so the answer is All of the above.It keeps a log of transactions for recovery (A), keeps before and after images of the database so that a transaction can be undone or redone (B), and applies concurrency control so that transactions running together do not interfere (C). Since each of those is one of its duties, any single option understates its role.

Q: Match the following :List - IList - IIa. Timeout ordering protocoli. Wait for graphb. Deadlock preventionii. Roll backc. Deadlock detectioniii. Wait-die schemed. Deadlock recoveryiv. Thomas Write RuleCodes : a b c d

The match is a-iv, b-iii, c-i, d-ii.The Thomas write rule belongs to timestamp (timeout) ordering. Wait-die is a deadlock prevention scheme. The wait-for graph is used to detect deadlock. Rolling back a transaction is how deadlock is recovered.Code (A) gives these pairs, while the other codes mismatch prevention, detection or recovery. The Thomas write rule lets an obsolete write be ignored in timestamp-based protocols, which is why it goes with the timeout ordering protocol, while deadlock prevention (wait-die and wound-wait), detection (wait-for graph) and recovery (rollback of a victim) are the three ways of dealing with deadlock.

Q: Locks placed by command are implicit locks.

Correct answer: FalseLocks placed by command are explicit; implicit locks are those the DBMS places on its own initiative to enforce the isolation level in force. The two terms classify locks by who asked for them, which is a different question from whether the lock is shared or exclusive.

Q: The size of a lock is referred to as lock sizing.

Correct answer: FalseThe term is lock granularity, not lock sizing. It describes whether the lock covers a row, a page, a table or the whole database, and the choice trades concurrency against the overhead of tracking a large number of locks.

Q: A cursor type in which the application sees the data as they were at the time the cursor was opened is called:

Correct answer: static.A static cursor takes a snapshot of the data when it is opened and shows that snapshot throughout, so changes made by others afterwards are invisible. It is the opposite of the dynamic cursor, and the keyset cursor sits between them, showing changes to the rows originally selected but not rows added later.

Q: Locks placed by command are called ________ .

Correct answer: explicit locksAn explicit lock is one the application asks for by issuing a command; an implicit lock is one the DBMS places on its own initiative to enforce isolation. The distinction is about who requests the lock. Shared and exclusive describe something different - what the lock permits others to do - so the two classifications are independent.

21.

A Transaction Manager is which of the following ?

A.Maintains a log of transactions
B.Maintains before and after database images
C.Maintains appropriate concurrency control
D.All of the above

Exam Year(s)

UGC NET - 2012,

Answer: D

A transaction manager does all three, so the answer is All of the above.

It keeps a log of transactions for recovery (A), keeps before and after images of the database so that a transaction can be undone or redone (B), and applies concurrency control so that transactions running together do not interfere (C). Since each of those is one of its duties, any single option understates its role.

Discuss in Forum

22.

What is Granularity ?

A.The size of database
B.The size of data item
C.The size of record
D.The size of file

Exam Year(s)

UGC NET - 2012,

Answer: B

Granularity, in database concurrency control, is the size of the data item that is locked or otherwise controlled as a unit, which can be a field value, a record, a disk block, a file or a whole database. Fine granularity means small items and permits more concurrent transactions, while coarse granularity means large items and less locking overhead. The sizes of the database, the record or the file are only some of the possible granules, so the general answer is the size of the data item, option (B).

Discuss in Forum

23.

The problem that occurs when one transaction updates a database item and then the transaction fails for some reason is ________.

A.Temporary Select Problem
B.Temporary Modify Problem
C.Dirty Read Problem
D.None

Exam Year(s)

UGC NET - 2012,

Answer: C

The problem in which one transaction updates a database item and then fails, so that the update is rolled back, while another transaction has already read the changed value, is the dirty read problem; some textbooks also call it the temporary update problem. The second transaction has then used a value that never existed in a committed state. Temporary select and temporary modify problems are not standard names for it. The answer is Dirty Read Problem, option (C).

Discuss in Forum

24.

Thoma's-write rule is ______.

A.Two phase locking protocol
B.Timestamp ordering protocol
C.One phase locking protocol
D.Sliding window protocol

Exam Year(s)

UGC NET - 2013,

Answer: B

Thomas' write rule is a part of the timestamp ordering protocol. It lets a write by an older transaction be ignored when a newer transaction has already written the item, which improves concurrency while keeping the schedule serialisable.

Two phase locking and one phase locking are lock-based protocols, and the sliding window protocol belongs to data transfer in networks. Option B is correct. Without the rule such a write would have to abort the transaction, but with it the obsolete write is skipped and the transaction continues.

Discuss in Forum

25.

Match the following :

List - I	List - II
a. Timeout ordering protocol	i. Wait for graph
b. Deadlock prevention	ii. Roll back
c. Deadlock detection	iii. Wait-die scheme
d. Deadlock recovery	iv. Thomas Write Rule

Codes : a b c d

A.iv iii i ii
B.iii ii iv i
C.ii i iv iii
D.iii i iv iii

Exam Year(s)

UGC NET - 2014,

Answer: A

The match is a-iv, b-iii, c-i, d-ii.

The Thomas write rule belongs to timestamp (timeout) ordering. Wait-die is a deadlock prevention scheme. The wait-for graph is used to detect deadlock. Rolling back a transaction is how deadlock is recovered.

Code (A) gives these pairs, while the other codes mismatch prevention, detection or recovery. The Thomas write rule lets an obsolete write be ignored in timestamp-based protocols, which is why it goes with the timeout ordering protocol, while deadlock prevention (wait-die and wound-wait), detection (wait-for graph) and recovery (rollback of a victim) are the three ways of dealing with deadlock.

Discuss in Forum

26.

Which of the following concurrency protocol ensures both conflict serializability and freedom from deadlock :

I. 2-phase locking
II. Time phase ordering

A.Both I & II
B.II only
C.I only
D.Neither I nor II

Exam Year(s)

UGC NET - 2014,

Answer: B

Only timestamp ordering (II) ensures conflict serializability and freedom from deadlock.

Two-phase locking guarantees conflict serializability but can deadlock because transactions wait for locks. Timestamp ordering never makes transactions wait and so it is deadlock free while being conflict serializable.

So the options with 2PL, which can deadlock, are wrong. Deadlock freedom in timestamp ordering comes from the rule that a transaction whose operation arrives too late is rolled back and restarted with a new timestamp, instead of being made to wait for another transaction.

Discuss in Forum

27.

Locks placed by command are implicit locks.

A.True
B.False

Answer: B

Correct answer: False

Locks placed by command are explicit; implicit locks are those the DBMS places on its own initiative to enforce the isolation level in force. The two terms classify locks by who asked for them, which is a different question from whether the lock is shared or exclusive.

Discuss in Forum

28.

The size of a lock is referred to as lock sizing.

A.True
B.False

Answer: B

Correct answer: False

The term is lock granularity, not lock sizing. It describes whether the lock covers a row, a page, a table or the whole database, and the choice trades concurrency against the overhead of tracking a large number of locks.

Discuss in Forum

29.

A cursor type in which the application sees the data as they were at the time the cursor was opened is called:

A.forward only.
B.static.
C.keyset.
D.dynamic.

Answer: B

Correct answer: static.

A static cursor takes a snapshot of the data when it is opened and shows that snapshot throughout, so changes made by others afterwards are invisible. It is the opposite of the dynamic cursor, and the keyset cursor sits between them, showing changes to the rows originally selected but not rows added later.

Discuss in Forum

30.

Locks placed by command are called ________ .

A.implicit locks
B.explicit locks
C.exclusive locks
D.shared locks

Answer: B

Correct answer: explicit locks

An explicit lock is one the application asks for by issuing a command; an implicit lock is one the DBMS places on its own initiative to enforce isolation. The distinction is about who requests the lock. Shared and exclusive describe something different - what the lock permits others to do - so the two classifications are independent.

Discuss in Forum

Loading…

Topics

Other Subjects

Tags: Managing Multiuser Databases Questions and Answers || Managing Multiuser Databases MCQ Questions and Answers || Managing Multiuser Databases GK Questions and Answers || Managing Multiuser Databases GK MCQ Questions || Managing Multiuser Databases Multiple Choice Questions and Answers || Managing Multiuser Databases GK || GK on Managing Multiuser Databases || Database Questions and Answers || Database MCQ Questions and Answers || Database GK Questions and Answers || GK on Database

Managing Multiuser Databases Questions and Answers

Topics

Other Subjects

About Us

Stay informed about all important Dates & Notifications