IIIT Hyderabad Practice Quiz : Databases-3

Consider the following locking protocol:
I. Transaction must lock all data items before begins any read or write operation.
II. Transaction executes all read and write operations along with transaction commit.
III. Transaction unlocks all data items.
Which of the following is true about given protocol?

Consider the following schedule S on 4 transactions i.e. T₁, T₂, T₃ and T₄ which are working on two data items namely A and B:

S: R₄(A), R₂(A), R₃(A), W₁(B), W₂(A), R₃(B), W₂(B)

Which of the following is correct?

Selecting the victim to be rollbacked to the previous state is determined by the minimum cost. The factors determining cost of rollback is

Why do we need concurrency control on B+ trees ?

A dense index containing 1024 entries can be converted to sparse index with 8 entries by-