Test: Transactions & Concurrency Control- 2


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15 Questions MCQ Test Question Bank for GATE Computer Science Engineering | Test: Transactions & Concurrency Control- 2

Test: Transactions & Concurrency Control- 2 for Computer Science Engineering (CSE) 2022 is part of Question Bank for GATE Computer Science Engineering preparation. The Test: Transactions & Concurrency Control- 2 questions and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus.The Test: Transactions & Concurrency Control- 2 MCQs are made for Computer Science Engineering (CSE) 2022 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Transactions & Concurrency Control- 2 below.
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Test: Transactions & Concurrency Control- 2 - Question 1

What is the goal of concurrency control protocol?

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 1

The goal of concurrency control protocol is schedule should be serializable.

Test: Transactions & Concurrency Control- 2 - Question 2

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

(i) 2 phase locking
(ii) Time stamp ordering

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 2

Time stamp ordering ensure both conflict serializability and free from deadlock.

Test: Transactions & Concurrency Control- 2 - Question 3

If the precedency graph of a given schedule is acyclic, then schedule

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 3

If the precedency graph of a given schedules is acyclis, then schedule will always be serializable.

Test: Transactions & Concurrency Control- 2 - Question 4

When n transactions are run concurrently and in an interleaved manner, the number of possible schedules are_________

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 4

When ‘n- transactions are runs concurrently then lower that n! interleaved schedules are possible.

Test: Transactions & Concurrency Control- 2 - Question 5

​In an DBMS without concurrency control, what consistency problem does the following transaction schedule depict?

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 5

For the given schedule transaction B reads a value R and is modified by Transaction A which one turn is again modified by Transaction B. In later time if Transaction B failed then the data modified due to transaction A is not recovered hence updation made by A is not matching with the recovered schedule.
Hence, lost update problem occurs.

Test: Transactions & Concurrency Control- 2 - Question 6

Consider the following log sequence of two transactions on a bank account, with initial balance 12000, that transfer 2000 to a mortage payment and, then apply a 5% interest.
1. T1 start
2. T1 B old = 12000 new = 10000
3. T1 M old = 0 new = 2000
4. T1 commit
5. T2 start
6. T2 Bold = 10000 new = 10500
​7. T2 commit

Suppose the database system crashed just before log record 7 is written. When the system is restarted, which one statement is true of the recovery procedure?

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 6

Given that the database system crashed just before log record 7 is written.
Since, before 7 T2 is not committed and T1, has committed. Therefore, T1, need not be redo log records 2 and 3.

Test: Transactions & Concurrency Control- 2 - Question 7

​Consider the following schedules involving two transactions. Which one of the following statements is TRUE?

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 7


Making the dependency graph for S1 and S2

According to the above graph we can easily see that
S1 is not conflict serializable but S2 is conflict serializable.

Test: Transactions & Concurrency Control- 2 - Question 8

​From transaction scenario given the precedence graph, which of the following is true?

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 8

Since cycle is present in given precedence graph. So transaction schedule is unserializable.

Test: Transactions & Concurrency Control- 2 - Question 9

Suppose that process P has been running for several days when a new process Q starts up and begins contending with Pfor resources. Which of the following is true?

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 9

Process P has been running for several days, when a new process Q starts-up and begins contending with P for resource.

Test: Transactions & Concurrency Control- 2 - Question 10

For the schedule given below, which of the following is correct?
1 Read A
2 Read B
3 Write A
4 Read A
5 Write A
6 Write B
7 Read B
8 Write B

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 10

Initial read of A is done by T1, whereas final write of B is also done by T1. Therefore W1(A), R2(A) and W2(B), R1 (B) are conflicting pairs. The schedule is neither T1 → T2 nor T2 →T1 serializable. Since schedule is not serializable, it can’t occur in a scheme using 2PL protocol.

Test: Transactions & Concurrency Control- 2 - Question 11

Consider three data items D1, D2, and D3, and the following execution schedule of transactions T1, T2 and T3. In the diagram, R(D) and W(D) denote the actions reading and writing the data item D respectively.

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 11

We have sequence W2(D2)→ W1(D1). Which means T2 →T1 whereas we also have W1(D1) →R2(D1) which means T1→ T2. Both are not possible. Therefore, schedule is not serializable.

Test: Transactions & Concurrency Control- 2 - Question 12

​Consider the following schedules involving two transactions. Which one of the following statements is TRUE?

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 12

Consider the table for transaction

There is no serializable conflict in transaction S1 but for statement w1(x) ; there is a conflict in S2 but it is also serializable.

Test: Transactions & Concurrency Control- 2 - Question 13

An index is clustered, if

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 13

Clustered index sort the data in the table based on their key values of the column on which clustered index is created.

Test: Transactions & Concurrency Control- 2 - Question 14

Consider two transactions T1 and T2, and four schedules S1 S2, S3, S4 of T1 and T2 as given below:

Which of the above schedules are conflict- serializable?

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 14

Schedule S2



Test: Transactions & Concurrency Control- 2 - Question 15

Consider the following four schedules due to three transactions (indicated by the subscript) using read and write on a data item x, denoted by r(x) and w(x) respectively. Which one of them is conflict serializable?

Detailed Solution for Test: Transactions & Concurrency Control- 2 - Question 15

r1(x); r2(x); w1(x); r3(x); w2(x)

Contains cycle; Not conflict serializable

Not contains cycle; conflict serializable.

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