University of Delhi 2010-2nd Sem M.C.A 1st yr DATABASE SYSTEMS AND IMPLEMENTATION UNIVERSITY - Question Paper

[This question paper contains 3 printed pages ]

6260-A    Your Roll No

M.Sc. COMPUTER SCIENCE/II Sem. J

MCS 203 - DATABASE SYSTEMS AND IMPLEMENTATION

(OC)

Time 2 hours    Maximum Marks 40

(Write your Roll No. on the top immediately on receipt of this question paper)

Attempt all questions Use of calculator is allowed Parts of a question should be answered together

1 (a) What are the advantages of RAID level 5 over RAID level 4 Explain with the help of an example    (3)

(b) Consider a disk with block size 512 bytes A block pointer is 6 bytes long, and a record pointer is 7 bytes long A file has 30,000 EMPLOYEE fixed length records ot 115 bytes each SSN is one of the fields in a record and occupies 9 bytes Suppose the file is ordered by the key field SSN and we want to construct a primary index on SSN Calculate

(i) the index blocking factor bfr_}

(ii) the number of first-level index entries and the number of first-level index blocks. Assume * that there is one index record for every block in the data file    (2)

(m) the number of levels needed if we make it into a multi-level index    (2)

(c) Consider a disk with the following characteristics: block size B * 512 bytes, interblock gap size 128 bytes, number of blocks per track = 20, number of tracks per surface = 400. A disk pack consists of 15 double-stded disks What is the total capacity of a cylinder and what is its useful capacity (excluding interblock gaps) ?    (2)

3    (a) Consider the following relational schema

Employee (personName, street, city) Works(personName, companyName, salary) Company(companyName, location)

Given the following relational algebra expression -

/    Emplcvee personName, Works companyNamt localton location-

city A saiarv, .ooooo (Employee tx] Works [XI Company)

Construct a relational algebra tree and a relational algebra expression that reflects the order of operations a query optimizer would choose for the given expression    (5)

(b) What is a transaction ? With the help of a diagram, explain the various states a transaction goes through    (5)