Test Papers / Previous Question Papers of IGNOU CS15 Relational Database Management System December 2002

MCA (III Yr)
Term-End Examination

December, 2002

CS15 : Relational Database Management System

Time: 3 hours
Maximum Marks: 75

1. (a) Draw an E-R diagram for conduct of examination by a university. The university has examination centers and student request/register for examination. The students are issued hall tickets. An examination center has many classrooms where examinations are conducted as per a defined schedule. Translate E-R model in the relational database which should be in 3NF.

(b) What are the weaknesses of SQL? Can a host language help SQL in overcoming these weaknesses? Justify your answer with the help of examples.

(c) “Redundancy is the backbone of reliability, therefore, a reliable database system should not attempt normalization beyond 3NF.” Comment on the above statement. Give reasons in support of or against the above statement. Use an example to justify your reasoning.

(d) Locking mechanism can be done at table level or at record level or at index level. Give advantages/disadvantages of locking a various levels. What is the need of having locking mechanism at various levels?

(e) What are the several forms of authorizing database users? Can a user pass his authorization to another user? How can you with draw an authorization?

2.
(a) consider a relation R (A, B, C, D, E, F, G, H) having the following set of dependencies:
{D®AB; B®A; C®A; F®G;H® fgd; E® A}

What are the candidate keys of relation R? The relation R is decomposed in R1 (A, B, H, D, E) and R2 (C, F, G, D, H). Is this decomposition loss less and dependency preserving?

(b) Does the data dictionary have any role to play in Query processing? Describe with the help of an SQL query requiring join operation, selection and projection.

(c) What is shadow paging mechanism? Describe with the help of an example. How is shadow paging different from log based recovery.

3.
(a) what is recovery? How is it related to information stored in loges file? How does a checkpoint help in the process of recovery? Describe with the help of an example.

(b) What is multi-valued dependency? What is fourth normal form? Describe with the help of an example. “A relation that has only two attributes, for example, (employee, dependent) where an employee has many dependents is in fourth normal form.” Comment on the above statement giving reason for or against the statement.

(c) What is the purpose of having statistical databases? What are the additional data security problems in statistical databases? Can audit trails help in solving the problem of data security problems of statistical databases? Justify your answer.

4.
(a) The relation R1 (A, B) (no. of records 2000) is to be joined to relation R2 (B, C) (no. of records 500). Assuming that the key to relation R1 is (A, B) and the key of R2 is B, estimate the size of the joined relation. Assuming that the number of buffers available for processing the join is 5 and the blocking factor for R1 and R2 both is 10 records per block, estimate the minimum number of block Transfers that will be required to join R1 and R2.

(b) What is serialisability? How does the locking mechanism ensure serialisability in concurrent transaction trying to access similar database records? Describe with the help of an example.

(c) “Views can be used in an attempt to implement logical data independence.” Comment on the above statement. Give justification and example in support of your answer. Where can you use views for data modifications?

5. (a) What are the advantages/disadvantages of hash indices relative to B-Tree indices? How does the available type of index influence the choice of query processing strategy?

(b) What the are the basic properties of transaction describe with the help of example. What are the components DBMS that may be assigned the responsibilities of ensuring the –violation of the transaction properties?

(c) What is timestamp? How can it be used to control the execution of concurrent transaction control.

6.
Describe the following in the context of distribute database management system and/or relation database management system with the help of example wherever needed:
(a) Distributes data storage
(b) Distribute data dictionary
(c) Deadlock handing
(d) Data warehousing
(d) Trigger