Database Management System Lecture - 22 © Virtual University of Pakistan

Data Volume and Usage Analysis Statistics about the size and usage of data plays critical role in data processing efficiency Final step of logical DB design or first step in physical DB design © Virtual University of Pakistan

Data Volume and Usage Analysis Statistics collected during analysis phase from the users of the system May not be accurate; give the tentative and relevant figures © Virtual University of Pakistan

Data Volume and Usage Analysis © Virtual University of Pakistan

© Virtual University of Pakistan Composite Usage Map PART 1000 MANUFAC-TURED PART PURCHASED PART O QUOTATION SUPPLIER 2500 40 % 70 % 50 140 200 60 40 80 75 (50) 70 700 400 © Virtual University of Pakistan

© Virtual University of Pakistan Designing Fields Field is smallest unit of application data; corresponds to a simple attribute Involves different decisions about fields © Virtual University of Pakistan

© Virtual University of Pakistan Choosing Data Type Data type is defined as set of values along with the operations that can be performed on them Precisely depends on the particular DBMS © Virtual University of Pakistan

© Virtual University of Pakistan Choosing Data Types Involves four objectives Minimize storage space Represent all possible values Improve data integrity Support all data manipulation © Virtual University of Pakistan

© Virtual University of Pakistan Coding Techniques Values of the attributes with small domains can be replaced by codes Codes can be stored in lookup table or can be hard coded, example © Virtual University of Pakistan

© Virtual University of Pakistan Coding Example stId stName hobby S1020 Sohail Dar Reading S1038 Shoaib Ali Gardening S1015 Tahira Ejaz Movies S1018 Arif Zia STUDENT © Virtual University of Pakistan

© Virtual University of Pakistan Coding Example STUDENT HOBBY stId stName hobby S1020 Sohail Dar R S1038 Shoaib Ali G S1015 Tahira Ejaz M S1018 Arif Zia code Hobby R Reading G Gardening M Movies © Virtual University of Pakistan

Controlling Data Integrity Concerns the possible values that a field can assume First such control is enforced by the data type Some others are… © Virtual University of Pakistan

Controlling Data Integrity Default value Range control Null values Referential integrity Handling missing data © Virtual University of Pakistan

Database Management System Lecture - 22 © Virtual University of Pakistan