(SEM-V) THEORY EXAMINATION 2019-20 DATA BASE MANAGEMENT SYSTEM

DATABASE MANAGEMENT SYSTEM (RCS-501)

B.Tech (SEM-V) – AKTU

SECTION A

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

Q1 (a) What is Relational Algebra?

Relational Algebra is a procedural query language used in DBMS to retrieve data from relations. It consists of a set of mathematical operations such as selection, projection, union, difference, and join, which operate on relations and produce new relations as output.

Q1 (b) Explain normalization. What is normal form?

Normalization is the process of organizing data in a database to reduce redundancy and avoid data anomalies. A normal form is a level of database normalization that determines the degree to which a table is normalized. Examples include 1NF, 2NF, and 3NF.

Q1 (c) What do you mean by aggregation?

Aggregation is a concept in ER modeling that represents a relationship between relationships. It is used when a relationship itself needs to participate in another relationship, allowing complex relationships to be modeled clearly.

Q1 (d) Define Super key, Candidate key, Primary key, and Foreign key.

A super key is a set of attributes that uniquely identify a record.
A candidate key is a minimal super key.
A primary key is a selected candidate key used for identification.
A foreign key is an attribute that references the primary key of another table.

Q1 (e) What is Strong and Weak entity set?

A strong entity set has a primary key and exists independently.
A weak entity set does not have a primary key and depends on a strong entity for identification.

Q1 (f) What do you mean by Conflict Serializable Schedule?

A conflict serializable schedule is a schedule that can be transformed into a serial schedule by swapping non-conflicting operations without changing the result of execution.

Q1 (g) Define Concurrency Control.

Concurrency control is the DBMS mechanism that ensures correct execution of concurrent transactions by maintaining database consistency and preventing conflicts such as lost updates and dirty reads.

SECTION B

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

Q2 (a) Explain data independence with its types.

Data independence refers to the ability to modify the database schema without affecting application programs.
Logical data independence allows changes in logical schema without affecting external schema.
Physical data independence allows changes in physical storage without affecting logical schema.

Q2 (b) Describe mapping constraints with its types.

Mapping constraints define relationships between entities in ER diagrams.
They include one-to-one, one-to-many, many-to-one, and many-to-many relationships. These constraints help maintain data integrity.

Q2 (d) Explain phantom phenomenon. Discuss Timestamp Protocol that avoids phantom problem.

The phantom phenomenon occurs when new rows inserted by a transaction appear in another transaction’s result set during execution.
Timestamp protocol assigns timestamps to transactions and ensures serializability by ordering execution based on timestamps, thereby preventing phantom reads.

SECTION C

(Attempt any one – 7 × 1 = 7 marks)

Q3 (a) Explain Directory System in detail.

A directory system in DBMS organizes files and data locations on storage devices. It maintains information such as file names, locations, sizes, and access rights. Directory systems improve data access efficiency, security, and file management by allowing structured storage and retrieval of database files.