Database Management System Questions and Answers

Answer: B

Correct answer: Base register addressing

With base register addressing every address in the code is an offset from a register loaded with the program's actual location, so moving the program means loading a different value into that register and changing nothing in the code itself. Indexed addressing exists to step through arrays and does not relocate anything.

Answer: D

Correct answer: record lock

A record lock is taken by the first transaction to reach the row, and the second must wait until it is released, so the two updates are serialised instead of overwriting each other. Passwords control who may connect, not what happens when two permitted users collide.

Answer: C

Correct answer: Entity instance

A particular set of attribute values describes one particular thing - one entity instance, or occurrence. The entity set is the collection of all such instances of the same type.

Answer: D

Correct answer: Select

Union, intersection and Cartesian product are all operations of set theory, applied here to relations. Selection is peculiar to relational algebra: it picks the tuples that satisfy a predicate, which set theory has no notion of.

Answer: A

Correct answer: Transaction management component of DBMS

Atomicity - all of a transaction's effects or none - is enforced by the transaction manager, which decides when to commit and calls for undo when a transaction aborts. Concurrency control provides isolation, a different one of the ACID properties.

Answer: A

Correct answer: 4,0

The difference \( A - B \) keeps A's columns, so the degree is still 4. It returns the tuples of A that are not in B, and every row of A is said to appear in B, so no rows remain.

Answer: C

Correct answer: idempotent

Recovery may be interrupted and restarted, so an undo or redo may be applied more than once to the same record. The operations are therefore written to be idempotent: applying them twice leaves the same result as applying them once.

Answer: D

Correct answer: Lost update problem

Update anomalies, insertion anomalies and redundancy are all consequences of a badly normalised design and would appear with a single user. The lost update problem arises from two transactions running at the same time, which is a concurrency issue.

Answer: C

Correct answer: transaction manager

The transaction manager ensures that every transaction takes the database from one consistent state to another, committing all of its changes or none of them. The buffer and file managers move pages, and the integrity manager checks constraints on individual operations.

Answer: A

Correct answer: Aggregation

Aggregation treats a relationship as though it were an entity, so that a further relationship can be attached to it. Without it there is no way to relate one relationship to another.