UNIVERSITY OF BOLTON WESTERN INTERNATIONAL COLLEGE FZE BSC (HONS) COMPUTING SEMESTER 1 EXAMINATIONS 2016/2017 ADVANCED DATABASE SYSTEMS

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1 OCD38 UNIVERSITY OF BOLTON WESTERN INTERNATIONAL COLLEGE FZE BSC (HONS) COMPUTING SEMESTER 1 EXAMINATIONS 2016/2017 ADVANCED DATABASE SYSTEMS MODULE NO: CPU6007 Date: Friday 13 th January 2017 Time: 2:00pm 4:00pm INSTRUCTIONS TO CANDIDATES: There are FIVEquestions. Answer ANY FOUR questions. All questions carry equal marks.

2 Page 2 of 7 Question 1 A multinational perfume company in Umm Al Quwain has an Oracle Database to handle its daily transactions with in UAE. Recently the senior management decided to open multiple warehouses and outlets in all the seven emirates. Before finalizing the move the senior management wants to know: Which products are increasing / decreasing in popularity, e.g. by analysing product sales over a year. The seasonality of products. The best customers. Product sales by region etc. You are supposed to be the database consultant for this company. (a) Suggest with justification a new database you may recommend for this company to answer the senior management queries so that they can take best business decisions. (b) Analyse the four basic characteristics of such database systems. (c) Compare the new database with the existing operational database. (10 marks) (d) Suggest appropriate ways to update data in such databases. Please turn the page

3 Page 3 of 7 Question 2 A Water Production&Distribution company in Dubai named DFWC has three divisions (such as Production, Transmission and Distribution) and 24 sites geographically distributed across the country. The company uses centralized legacy database systems to run financial applications, engineering maintenance management application, inventory management, Geographic Information System, and utility billing systems. Presently DFWC has the following issues with the legacy systems. These sites cannot share any data between each other and there is no local control of data. Sites face frequent network link failure and loss of mission critical billing service. Meets with a data growth of at least 25% per year. Also more sites are expected to be added in future. Has last 12 years of data in its legacy system.this huge volume data is vital and still in use for asset maintenance history reporting, consumer deposit history reporting etc. Faces huge performance degradation during peak usage hours. DFWC decided to implement a modern distributed database system as its first move towards an integrated system. (a) Analyse at least five benefits DFWC gets from its current decision. (10 marks) (b) To the user, a distributed system should look exactly like a NON-distributed system. Analyse the four main types of transparencies provided by distributed database management systems (DDBMS), in order to accomplish this fundamental principle. Question 2 Continued over the page

4 Page 4 of 7 Question 2 continued (c) Propose with the aid of examples when it may be appropriate to use horizontal fragmentation or vertical fragmentation in DDBMS. (d) Analyse two phase commit protocol (2PC). (e) Compile the four phases of distributed query processing. Question 3 (a) ACID properties are essential for all transactions in database. Analyse how transactions, failures and recovery support ACID concept do. (b) Justify why databases need concurrency and concurrency control, and discuss the three problems caused by concurrency. (c) Discuss the lost update problem in the context of the following two transactionst1 and T2 in table1, and suggest whether these transactions are serializable or not. Table 1 Time T1 T2 bal x t1 begin_transaction 100 t2 begin_transaction read(bal x) 100 t3 read(bal x) bal x= bal x t4 bal x = bal x-10 Write(bal x) 200 t5 Write(bal x) Commit 90 t6 Commit 90 (5 marks) Question 3 Continued over the page

5 Page 5 of 7 Question 3 continued (d) Analyse the behaviour of 2-phase locking (2PL) protocol. (e) Using the example in Table1shown above,explain how 2-phase locking will guarantee the prevention of lost update problem. (f) A major problem of locking mechanism is dead lock. Create an example of two transactions T3 and T4 to demonstrate deadlock and discuss a method to resolve deadlock. Question 4 (a) Analyse the uses of PL/SQL with different options available to store user defined PL/SQL. (b) The exception handler is used to handle errors in a graceful way. Discuss the need for and the use of exceptions in PL/SQL. (c) Analyse the differences in the privileges required between using: (i) A trigger defined on insert into a table to fire some PL/SQL code, and (ii) A procedure that does the same insert into the table and executes similar PL/SQL code to do the same functionality. Question 4 Continued over the page

6 Page 6 of 7 Question 4 continued (d) When an employee joins in a department, the employee may not be allocated to a section, but once allocated and recorded in the Joining table, an employee should never be without a section. So any updates on the Employee s section on the joining table should never leave the Employee without a section. The following trigger works to enforce the above constraint:- CREATE TRIGGER update-section BEFORE UPDATE OF section-id ON joining FOR EACH ROW IF (NEW.section_id IS NULL) THEN RAISE_APPLICATION_ERROR (-20200, No Section Allocated ) END IF; (i) Analyse the circumstances under which the above trigger is invoked and how it works. (ii) Triggers can be used to pull data from other tables into non-base-table fields on a form. With the aid of an example from the case study used in the course,discuss how to achieve this and the advantages of doing this for the userof theform. (e) With the aid of examples discuss how triggers can be used to: Supplement declarative constraints to maintain database integrity Enforce complex business rules Audit changes to data Please turn the page

7 Page 7 of 7 Question 5 (a) Analyse Query Processing with aims, phases and optimizations. (b) Compare and contrast the two approaches Oracle uses to optimize queries. (c) Analyse the mainbenefits of database replication. (d) To create and maintain a Data Warehouse requires operational data to be extracted, transformed and loaded to it. Discuss in detail the four processes involved. (7 marks) (e) Data mining attempts to discover hidden and unexpected patterns / relationships within a warehouse with the use of appropriate software tools. Analyse the four main operations associated with data mining. END OF QUESTIONS