(SEM 5th) THEORY EXAMINATION 2018-19 DATABASE MANAGEMENT SYSTEM

DATABASE MANAGEMENT SYSTEM (RCS-501)

B.Tech (SEM-V) – AKTU
                                                                                               Time: 3 Hours  Total Marks: 70

SECTION A

(Attempt all questions in brief – 2 × 7 = 14 marks)

Q1 (a) What is data abstraction? Explain its levels.

Data abstraction is the process of hiding complex database details from users and showing only relevant information.
There are threethree levels of data abstraction:
Physical level describes how data is stored on disk, logical level describes what data is stored and relationships, and view level describes user-specific views of data.

Q1 (b) What is a transaction? State its properties.

A transaction is a sequence of database operations treated as a single unit of work.
Its properties are called ACID properties: Atomicity, Consistency, Isolation, and Durability, which ensure reliable database processing.

Q1 (c) Define functional dependency.

Functional dependency is a relationship between two sets of attributes in a relation, where one attribute uniquely determines another.
It is represented as A → B, meaning B is functionally dependent on A.

Q1 (d) What is normalization?

Normalization is the process of organizing database tables to reduce redundancy and dependency.
It improves data consistency and efficiency by dividing large tables into smaller related tables.

Q1 (e) Define serial schedule.

A serial schedule is a schedule in which transactions are executed one after another without interleaving.
It ensures database consistency but may reduce performance.

Q1 (f) What is deadlock?

Deadlock occurs when two or more transactions wait indefinitely for resources held by each other.
As a result, none of the transactions can proceed.

Q1 (g) What is indexing?

Indexing is a technique used to speed up data retrieval operations in a database.
It creates a data structure that allows faster searching without scanning the entire table.

SECTION B

(Attempt any three – 7 × 3 = 21 marks)

Q2 (a) Explain ER model with suitable example.

The Entity Relationship (ER) model is a conceptual database model used to represent data and relationships visually.
Entities represent real-world objects, attributes represent properties, and relationships show associations between entities.

For example, a Student entity may have attributes like Roll No, Name, and Course, and can have a relationship with Subject entity.

**Q2 (b) Define minimal cover. Suppose a relation R(A, B, C) has FD set

F = {A → B, B → C, A → C, AB → B, AB → C, AC → B}. Convert this FD set into minimal cover.**

Minimal cover is the smallest equivalent set of functional dependencies that preserves the same closure.

After removing redundant dependencies and attributes, the minimal cover is:
{A → B, B → C}

Q2 (c) Explain different types of normalization forms.

First Normal Form (1NF) removes multivalued attributes.
Second Normal Form (2NF) removes partial dependency.
Third Normal Form (3NF) removes transitive dependency.
Boyce-Codd Normal Form (BCNF) is a stronger version of 3NF that removes all anomalies.

Q2 (d) Explain file organization techniques.

File organization refers to how records are stored on disk.
Types include sequential file organization, direct file organization, indexed file organization, and hashing.
Proper file organization improves storage efficiency and retrieval speed.

SECTION C

(Attempt any one part from each question – 7 × 2 = 14 marks)

Q5 (a) Explain Two Phase Locking Protocol with suitable example.

Two Phase Locking (2PL) protocol ensures serializability by dividing transaction execution into two phases:
Growing phase, where locks are acquired, and shrinking phase, where locks are released.

Example:
Transaction T1 locks data item A and B before releasing any lock, ensuring conflict-free execution.

Q5 (b) Write the salient features of graph-based locking protocol with suitable example.

Graph-based locking protocol uses a directed graph to define lock acquisition order.
A transaction can lock a data item only if all its parent nodes are already locked.
This protocol avoids deadlock and ensures serializability.

Q6 (a) Which of the following schedules are conflict serializable? For each serializable schedule find the equivalent schedule.

S1: r1(x) r3(x) w3(x) w1(x) r2(x)
S2: r3(x) r2(x) w3(x) r1(x) w1(x)

By constructing precedence graphs:
S1 is conflict serializable and equivalent to T3 → T1 → T2
S2 is not conflict serializable due to cycle in precedence graph.