GATE CSE 2024 Set 2 | Transactions and Concurrency Question 2 | Database Management System

GATE CSE 2024 Set 2

MCQ (More than One Correct Answer)

-0.33

Which of the following statements about the Two Phase Locking (2PL) protocol is/are TRUE?

2PL permits only serializable schedules

With 2PL, a transaction always locks the data item being read or written just before every operation and always releases the lock just after the operation

With 2PL, once a lock is released on any data item inside a transaction, no more locks on any data item can be obtained inside that transaction

A deadlock is possible with 2PL

GATE CSE 2022

MCQ (Single Correct Answer)

-0.33

Let R_i(z) and W_i(z) denote reac and write operations on a data element z by a transaction T_i, respectively. Consider the schedule S with four transactions.

S : R₄(x), R₂(x), R₃(x), R₁(y), W₁(y), W₂(x), W₃(y), R₄(y)

Which one of the following serial schedules is conflict equivalent to S?

T₁ $$\to$$ T₃ $$\to$$ T₄ $$\to$$ T₂

T₁ $$\to$$ T₄ $$\to$$ T₃ $$\to$$ T₂

T₄ $$\to$$ T₁ $$\to$$ T₃ $$\to$$ T₂

T₃ $$\to$$ T₁ $$\to$$ T₄ $$\to$$ T₂

GATE CSE 2019

MCQ (Single Correct Answer)

-0.33

Consider the following two statements about database transaction schedules:

I. Strict two-phase locking protocol generates conflict serializable schedules that are also recoverable.

II. Timestamp-ordering concurrency control protocol with Thomas Write Rule can generate view serializable schedules that are not conflict serializable.

Which of the above statements is/are TRUE?

Both I and II

I only

II only

Neither I nor II

GATE CSE 2016 Set 2

MCQ (Single Correct Answer)

-0.3

Suppose a database schedule $$S$$ involves transactions $${T_1},\,...,\,{T_n}.$$ Construct the precedence graph of $$S$$ with vertices representing the transactions and edges representing the conflicts. If $$S$$ is serializable, which one of the following orderings of the vertices of the precedence graph is guaranteed to yield a serial schedule?

Topological order

Depth-first order

Breadth-first order

Ascending order of transaction indices

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