1. Chapter 3 The Database Management System Concept
Fundamentals of Database Management Systems, 2nd ed by
Mark L. Gillenson, Ph.D.
University of Memphis
John Wiley & Sons, Inc.

2. Chapter Objectives
Discuss the problems encountered in a nondatabase information systems environment.
Discuss the nature of data.
Define data-related terms such as entity and attribute.

3. Chapter Objectives
Define storage-related terms such as field, record, and file.
Identify the four basic operations performed on stored data.
Compare sequential access of data with direct access of data.

4. Chapter Objectives
List the five basic principles of the database concept.
Describe how data can be considered to be a manageable resource.

5. Chapter Objectives List the three problems created by data redundancy.
Describe the nature of data redundancy among many files.
Explain the relationship between data integration and data redundancy in one file.

6. Chapter Objectives
State the primary defining feature of a database management system.
Explain why the ability to store multiple relationships is an important feature of the database approach.

7. Chapter Objectives
Explain why providing support for such control issues as data security, backup and recovery, and concurrency is an important feature of the database approach.
Explain why providing support for data independence is an important feature of the database approach.

8. Data Processing Systems
Data was stored in different formats in different files.
Data was often not shared among different programs that needed it, necessitating the duplication of data in redundant files.
Little was understood about file design, resulting in redundant data within individual files.

9. Data Processing Systems
Files often could not be rebuilt after being damaged by a software error or a hardware failure.
Data was not secure and was vulnerable to theft or malicious mischief by people inside or outside of the company.

10. Data Processing Systems
Programs were usually written in such a manner that if the way that the data was stored changed, the program had to be modified to continue working.
Changes in everything from access methods to tax tables required programming changes.

11. Data Before Database Management Records and Files
Entity - a “thing” or “object” in our environment that we want to keep track of.
Entity set - A collection of entities of the same type (e.g., all of the company’s employees).

12. Records and Files
Attribute - a property of, a characteristic of, or a fact that we know about an entity.
Some attributes have unique values within an entity set.

13. Records and Files key field
Record - each row of a structure like above
Fields - the columns, representing the facts
File - the entire structure

14. Records and Files
Record type - a structural description of each and every record in the file
Record occurrence / Record instance - a specific record of the salesperson file

15. Retrieving and Manipulating Data
Four fundamental operations can be performed on stored data:
Retrieve or Read - looking at a record’s contents without changing it
Insert - adding a new record to the file, as when a new salesperson is hired
Delete - deleting a record from the file, as when a salesperson leaves the company
Update - changing one or more of a record’s field values

16. Data Retrieval Method
Sequential access - the retrieval of all or a portion of the records of a file one after another, in some sequence, starting from the beginning, until all of the required records have been retrieved.
Physical sequential access - records are retrieved, one after the other, just as they are stored on the disk device.
Logical sequential access - records are retrieved in an order based on the values of one or a combination of the fields.

17. Data Retrieval Method
Direct Access - the retrieval of a single record of a file or a subset of the records of a file based on one or more values of a field or a combination of fields in the file.
a crucial concept in information systems today
requires hardware storage device that will accommodate direct access
requires software that will take advantage of the hardware’s capabilities and store and retrieve the data in such a way that it accomplishes direct access.

18. The Database Concept 1. Data as a Manageable Resource
2. Data Integration and Data Redundancy
3. Multiple Relationships
4. Data Control Issues
5. Data Independence

19. The Database Concept
Data as a Manageable Resource - The creation of a data-centric environment in which a company’s data can truly be thought of as a significant corporate resource. A key feature of this environment is the ability to share data among those inside and outside of the company who require access to it.

20. The Database Concept
Data Integration and Data Redundancy - The ability to achieve data integration while at the same time storing data in a nonredundant fashion. This, alone, is the central, defining feature of the database approach.
Multiple Relationships - The ability to store data representing entities involved in multiple relationships without introducing data redundancy or other structural problems.

21. The Database Concept
Data Control Issues - The establishment of an environment that manages certain data control issues, such as data security, backup and recovery, and concurrency control.
Data Independence - The establishment of an environment that permits a high degree of data independence.

22. Data as a Manageable Resource
Information systems environment:
Hardware
Networks
Applications software
Systems software
People
Data

23. Data as a Manageable Resource
Historically, data has not been the highest priority concern.
As the operational, tactical, and strategic corporate levels became more dependent on information systems, data increasingly became recognized as an important corporate resource.

24. Data as a Manageable Resource
The corporate community became increasingly convinced that a firm’s data could provide a significant competitive advantage to the firm.
It became clear that data would have to be managed in an organized way.

25. Data as a Manageable Resource

26. Data as a Manageable Resource
Needed a software utility that could manage and protect data.
Data could be a critical corporate resource.
Out of this need was born the database management system.

27. Data as a Manageable Resource
Reengineering - data is aggressively used to redesign business processes.
Electronic commerce - a database at the heart of every web site; allows companies and customers to conduct business.
ERP systems - collections of application programs build around a central database.

28. Data Integration and Data Redundancy
Data integration - the ability to tie together pieces of related data within an information system.
Data redundancy - the same fact about the business environment is stored more than once within an information system.

29. Data Redundancy - Problems
Redundant data takes up a great deal of extra disk space.
If the redundant data has to be updated, it takes additional time to do so. This can be a major performance issue.
There is the potential for data integrity problems.

30. Data Integrity Refers to the accuracy of the data.
Inaccurate data leaves the whole information system of limited value.

31. Data Redundancy, Data Integrity
When all copies of redundant data are not updated consistently, a data integrity problem exists.

32. Three Files with Redundant Data

33. Three Files with a Data Integrity Problem

34. General Hardware Company Files

35. General Hardware Company Combined File
Customer
Number
Name
Salesperson
HQ City
Commission %
Year
of Hire

36. Anomalies Typically occur in poorly structured files.
Problems arise when two different kinds of data, like salesperson and customer data are merged into one file.

37. Anomalies
Deletion Anomaly - e.g, if you delete a customer and that record was the only one for a salesperson, the salesperson’s data is gone.
Insertion Anomaly - e.g., General Hardware cannot add data about a new salesperson the company just hired until she is assigned at least one customer.
Update Anomaly - redundant data in the database file must be updated each place it exists when it changes.

38. Database Management System
A software utility for storing and retrieving data that gives the end-user the impression that the data is well integrated even though the data can be stored with no redundancy at all.

39. Multiple Relationships - Horizontal Solution

40. Multiple Relationships - Vertical Solution

41. Data Control Issues Data security Backup and Recovery
Concurrency Control

42. Computer Security A very broad topic
Protecting the physical hardware environment
Defending against hacker attacks
Encrypting data transmitted over networks
Educating employees on the importance of protecting the company’s data
… and many more

43. Backup and Recovery
Data can be lost or corrupted in any of a variety of ways:
a disaster such as a fire, a hurricane, or an earthquake
hackers
computer viruses
poorly written application programs
unintentional error

44. Concurrency Problem
Updates to a database can interfere with each other in such a way that the resulting data values will be incorrect.
A database management system must be designed to protect its databases from such an eventuality.

45. Data Independence
Data Dependence - if for any reason the storage characteristics of the data had to be changed, the application program itself had to be modified, often extensively.
Data Independence - to have a data storage and programming environment in which as many types of changes in the data structure as possible would not require changes in the application programs that use them.

46. Major DBMS Approaches Hierarchical - navigational
Network - navigational
Relational - became commercially viable in about 1980.
Object-oriented - useful for a variety of niche applications.

47. Hierarchical & Network
Called navigational approaches because of the way that programs have to “navigate” through hierarchies and networks of data to find needed data.
Developed in the 1960s and 1970s.
Somewhat similar in structure.

48. Hierarchical & Network
Suitable only for mainframe computers
were an elegant solution to the redundancy/integration problem at the time
Complex, difficult to work
Now considered legacy systems

49. Relational Database Became commercially viable in about 1980
Soon became the preferred DBMS approach and it has remained so ever since.

50. Object-oriented Has proven useful for a variety of niche applications
It is interesting to note that some of the key object-oriented database concepts have found their way into some of the mainstream relational DBMSs and some are described as taking a hybrid object/relational approach to database.

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