Database Management System Back Paper 2017-18 Solution
Short Questions

Q1. Answer the following questions: [Marks: 2 x 10]

a) Define Atomicity in transaction management.

Ans: Atomicity in DBMS means a series of operation that cannot occur partially. It can either occur fully or not occur at all.

b) What is the function of DBA?

Ans: A database administrator (DBA) is an individual person or group of persons with an overview of one or more databases that control the design and the use of these databases.

These are the functions of a database administrator:

  1. Defining conceptual schema and database creation
  2. Storage structure and access-method definition
  3. Granting authorization to the users
  4. Physical organization modification
  5. Job monitoring

c) What do you mean by weak entity set?

Ans: A weak entity set is an entity set that does not contain sufficient attributes to uniquely identify its entities. In other words, a primary key does not exist for a weak entity set.

d) What are the ACID properties?

Ans:transaction is a set of logically related operations. To maintain the integrity of a database, all transactions must obey ACID properties. ACID is an acronym for atomicity, consistency, isolation, and durability.

e) What is normalization?

Ans:  Normalization is a database design technique that is used to minimize the redundancy and dependency of data. Normalization divides larger tables into smaller tables and links them using relationships.

f) Write a note on functional dependencies.

Ans: A functional dependency (FD) is a relationship between two attributes, typically between the PK and other non-key attributes within a table.

For any relation R, attribute Y is functionally dependent on attribute X (usually the PK), if for every valid instance of X, that value of X uniquely determines the value of Y. This relationship is indicated by the representation shown below :

X ——–> Y

The left side of the above FD diagram is called the determinant, and the right side is the dependent.

g) Distinguish between sparse index and dense index.

Ans: Difference between sparse index and dense index:

Dense IndexSparse Index
1. In Dense Index, an index entry appears for every search-key1. In Sparse index, an index entry appears for only some of the search-key values.
2. This record contains search key value and a pointer to the actual record.2. To locate a record, we find the index record with the largest search key value less than or equal to the search key value we are looking for.
3. The index size is large3. The index size is small.

h) List the two commonly used Concurrency Controlled techniques.

Ans: Commonly used concurrency controlled techniques are:

  1. Two-phase locking protocol
  2. Time stamp ordering protocol

i) What are the advantage and disadvantage of indexed sequential file?

Ans: Advantages:

  1. Reading of records in order of the ordering key is extremely efficient.
  2. Finding the next record in order of the ordering key usually, does not require additional block access.Moreover, Next record may found in the same block.
  3. Its simple to program and easy to design.

Disadvantages:

  1. The sequential file does not give any advantage when the search operation is to carry out in non-ordering field.
  2. Insertion, deletion of a record is an expensive operation.
  3. Sequential file is time consuming process.
  4. It has high data redundancy.
  5. Random searching is not possible.

j) Define database tuning.

Ans: Database tuning refers to a set of activities and procedures that reduce response time of database system..