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# GATE CS 2021 : Database Quiz 7 (App update required to attempt this test)

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Question 1

A transaction state changes from active to______, after the transaction has been rolled back and the database restored to its state prior to the start of the transaction

Question 2

When transaction Ti requests a data item currently held by Tj, Ti is allowed to wait only if it has a timestamp smaller than that of Tj (that is, Ti is older than Tj). Otherwise, Ti is rolled back (dies). This is

Question 3

How many of the following schedules are conflict serializable?

I. r1(A), w1(B), r2(B), w2(C), r3(C), w3(A)

II. w3(A), r1(A), w1(B), r2(B), w2(C), r3(C)

III. r1(A), r2(A), w1(B), w2(B), r1(B), r2(B), w2(C), w1(D)

IV. r1(A), r2(A), r1(B), r2(B), r3(A), r4(B), w1(A), w2(B)

Question 4

Consider the following statements about transactions:

I. The transaction is executed as a single unit

II. If the database were in an inconsistent state before a transaction, it can go to consistent state after the transaction.

III. If the database operations do not update the database but only retrieve data, this type of transaction is called a read-only transaction.

IV. The terminated state refers to the transaction leaving the system.

The number of incorrect statement/s are:

Question 5

Consider transaction and which are defined as: : read(A);

A = A – 50;

write(A);

B : = B + 50;

Write(B); : read(C);

C: = C – 100;

Write(C);

A, B, C before execution were Rs. 1000, Rs. 2000, Rs. 700 respectively and the system crash occurs after write (B), then which of the following is correct?

Question 6

Topological order for a directed acyclic graph is the order in which vertices of the graph are visited. It is possible to have more than topological order for a given Graph

Let N be the no of vertices in a particular graph with zero edges, than, how many topological orders are possible for the graph if n= 4 _______.

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