REV 00 Chapter 1 Introduction to Databases DDC

REV 00 Chapter 1 Introduction to Databases DDC 2483 DATABASE SYSTEM 1

Examples of Database Systems • • • REV 00 Purchases from the supermarket Purchases using your credit card Booking a holiday at the travel agents Using the local library Renting a video Using the Internet DDC 2483 DATABASE SYSTEM 2

Database REV 00 • Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization. DDC 2483 DATABASE SYSTEM 3

Database REV 00 • Shared collection – can be used simultaneously by many departments and users. • Logically related - comprises the important objects and the relationships between these objects. • Description of the data – the system catalog (meta-data) provides description of data to enable data independence. DDC 2483 DATABASE SYSTEM 4

DBMS REV 00 • A software system that enables users to define, create, and maintain the database and that provides controlled access to this database. DDC 2483 DATABASE SYSTEM 5

DBMS DDC 2483 DATABASE SYSTEM REV 00 6

REV 00 Components of DBMS Environment • Hardware – Can range from a PC to a network of computers. • Software – DBMS, operating system, network software (if necessary) and also the application programs. • Data – Used by the organization and a description of this data called the schema. DDC 2483 DATABASE SYSTEM 7

Functions of a DBMS REV 00 • Data Storage, Retrieval, and Update. • A User-Accessible Catalog. • Transaction Support. • Concurrency Control Services. • Recovery Services. DDC 2483 DATABASE SYSTEM 8

Functions of a DBMS REV 00 • Authorization Services. • Support for Data Communication. • Integrity Services. • Services to Promote Data Independence. • Utility Services. DDC 2483 DATABASE SYSTEM 9

Advantages of DBMSs • • • REV 00 Control of data redundancy Data consistency Sharing of data Improved data integrity Improved maintenance through data independence. DDC 2483 DATABASE SYSTEM 10

Disadvantages of DBMSs • • • REV 00 Complexity Cost of DBMS Cost of conversion Performance Higher impact of a failure DDC 2483 DATABASE SYSTEM 11