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Chapter 1

   Introduction to Databases
        Transparencies


            © Pearson Education Limited,
                ...
Chapter 1 - Objectives
   Common uses of database systems.
   Meaning of the term database.
   Meaning of the term Data...
Examples of Database Systems
   Purchases from the supermarket
   Purchases using your credit card
   Booking a holiday...
Database
   Shared collection of logically related
    data (and a description of this data),
    designed to meet the in...
Database
   Shared collection – can be used
    simultaneously by many departments
    and users.
   Logically related -...
DBMS
   A software system that enables users
    to define, create, and maintain the
    database     and     that     pr...
Database application program
   A software program that interacts
    with the database by issuing an
    appropriate req...
Views
   Allows each user to have his or her
    own view of the database.

   A view is essentially some subset of
    ...
Views
   Benefits include:
       Provide a level of security;
       Provide a mechanism to customize the
        appe...
DBMS




       © Pearson Education Limited,
                  2004                10
Components of DBMS
    Environment
   Hardware
       Can range from a PC to a network of
        computers.
   Softwar...
Components of DBMS
    Environment
   Procedures
       Instructions and rules that should be
        applied to the des...
Two-Tier Client-Server
   Client manages main business and
    data processing logic and user
    interface.
   Server m...
Two-Tier Client-Server




         © Pearson Education Limited,
                    2004                14
Three-Tier C-S Architecture
   Client side presented two problems
    preventing true scalability:
       ‘Fat’ client, ...
Three-Tier C-S Architecture
   User interface layer – runs on client.
   Business logic and data processing
    layer – ...
Three-Tier C-S Architecture
   Advantages:
       ‘Thin’ client, requiring less expensive
        hardware.
       Appl...
Three-Tier C-S Architecture




         © Pearson Education Limited,
                    2004                18
Functions of a DBMS
   Data Storage, Retrieval, and Update.
   A User-Accessible Catalog.
   Transaction Support.
   C...
Functions of a DBMS
   Authorization Services.
   Support for Data Communication.
   Integrity Services.
   Services t...
Advantages of DBMSs
   Control of data redundancy
   Data consistency
   Sharing of data
   Improved data integrity
 ...
Disadvantages of DBMSs
   Complexity
   Cost of DBMS
   Cost of conversion
   Performance
   Higher impact of a failu...
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  1. 1. Chapter 1 Introduction to Databases Transparencies © Pearson Education Limited, 2004 1
  2. 2. Chapter 1 - Objectives  Common uses of database systems.  Meaning of the term database.  Meaning of the term Database Management System (DBMS).  Components of the DBMS environment.  Typical functions of a DBMS.  Advantages/disadvantages of DBMSs. © Pearson Education Limited, 2004 2
  3. 3. Examples of Database Systems  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 © Pearson Education Limited, 2004 3
  4. 4. Database  Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization. © Pearson Education Limited, 2004 4
  5. 5. Database  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.© Pearson Education Limited, 2004 5
  6. 6. DBMS  A software system that enables users to define, create, and maintain the database and that provides controlled access to this database. © Pearson Education Limited, 2004 6
  7. 7. Database application program  A software program that interacts with the database by issuing an appropriate request (typically an SQL statement) to the DBMS. © Pearson Education Limited, 2004 7
  8. 8. Views  Allows each user to have his or her own view of the database.  A view is essentially some subset of the database. © Pearson Education Limited, 2004 8
  9. 9. Views  Benefits include:  Provide a level of security;  Provide a mechanism to customize the appearance of the database;  Present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed. © Pearson Education Limited, 2004 9
  10. 10. DBMS © Pearson Education Limited, 2004 10
  11. 11. 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. © Pearson Education Limited, 2004 11
  12. 12. Components of DBMS Environment  Procedures  Instructions and rules that should be applied to the design and use of the database and DBMS.  People  Includes database designers, DBAs, application programmers, and end-users. © Pearson Education Limited, 2004 12
  13. 13. Two-Tier Client-Server  Client manages main business and data processing logic and user interface.  Server manages and controls access to database. © Pearson Education Limited, 2004 13
  14. 14. Two-Tier Client-Server © Pearson Education Limited, 2004 14
  15. 15. Three-Tier C-S Architecture  Client side presented two problems preventing true scalability:  ‘Fat’ client, requiring considerable resources on client’s computer to run effectively.  Significant client side administration overhead.  By 1995, three layers proposed, each potentially running on a different platform. © Pearson Education Limited, 2004 15
  16. 16. Three-Tier C-S Architecture  User interface layer – runs on client.  Business logic and data processing layer – middle tier runs on a server (application server).  DBMS – stores data required by the middle tier. This tier may be on a separate server (database server). © Pearson Education Limited, 2004 16
  17. 17. Three-Tier C-S Architecture  Advantages:  ‘Thin’ client, requiring less expensive hardware.  Application maintenance centralized.  Easier to modify or replace one tier without affecting others.  Separating business logic from database functions makes it easier to implement load balancing.  Maps quite naturally to Web environment. © Pearson Education Limited, 2004 17
  18. 18. Three-Tier C-S Architecture © Pearson Education Limited, 2004 18
  19. 19. Functions of a DBMS  Data Storage, Retrieval, and Update.  A User-Accessible Catalog.  Transaction Support.  Concurrency Control Services.  Recovery Services. © Pearson Education Limited, 2004 19
  20. 20. Functions of a DBMS  Authorization Services.  Support for Data Communication.  Integrity Services.  Services to Promote Data Independence.  Utility Services. © Pearson Education Limited, 2004 20
  21. 21. Advantages of DBMSs  Control of data redundancy  Data consistency  Sharing of data  Improved data integrity  Improved maintenance through data independence. © Pearson Education Limited, 2004 21
  22. 22. Disadvantages of DBMSs  Complexity  Cost of DBMS  Cost of conversion  Performance  Higher impact of a failure © Pearson Education Limited, 2004 22
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