a) What problem can occur in a distributed system due to the failure of link and partitioning
of the network? What are the ways by which recovery can take place?
[10 Marks]
b) X, Y and Z are all relations with a single attribute A. A naıve user wishes to compute the
set-theoretic expression X∩(Y∪Z) and writes the following SQL query.
SELECT X.A FROM X, Y, Z WHERE X. A=Y.A OR X. A=Z.A
i) Give the relational algebra term that this query would be compiled to. [3 Marks]
ii) Does the SQL query satisfy the user’s expectation? Justify your answer.
[4 Marks]
c) A high street bank has just announced a merger with a nationwide building society. You
are employed as a consultant to advise on the integration of their client databases. Both
institutions use relational databases. Write brief notes to alert the database administrators
to the difficulties that they may encounter.
[8 Marks]
QUESTON TWO
a) Using a case as an example describe the various techniques that are used to implement
distributed databases concepts shown in the diagram below
[14 Marks]
b) Give an example of a set of requirements whose solution would need to combine OLAP,
OLTP and NoSQL. Describe an architecture integrating these elements in the distributed
databases system design.
[11 Marks]