File Systems and Databases

1. Chapter 1 File Systems and Databases Prof. Sin-Min Lee Dept. of Computer Science

2. Introducing the Database • Major Database Concepts • Data and information • Data - Raw facts • Information - Processed data • Data management • Database • Metadata • Database management system (DBMS)

4. Sales per Employee for Each of ROBCOR’S Two Divisions Figure 1.1

9. Introducing the Database • Importance of DBMS • It helps make data management more efficient and effective. • Its query language allows quick answers to ad hoc queries. • It provides end users better access to more and better-managed data. • It promotes an integrated view of organization’s operations -- “big picture.” • It reduces the probability of inconsistent data.

11. The DBMS Manages the Interaction Between the End User and the Database Figure 1.2

13. Introducing the Database • Why Database Design Is Important? • A well-designed database facilitates data management and becomes a valuable information generator. • A poorly designed database is a breeding ground for uncontrolled data redundancies. • A poorly designed database generates errors that lead to bad decisions.

18. Historical Roots • Why Study File Systems? • It provides historical perspective. • It teaches lessons to avoid pitfalls of data management. • Its simple characteristics facilitate understanding of the design complexity of a database. • It provides useful knowledge for converting a file system to a database system.

19. Contents of the CUSTOMER File Figure 1.3

22. Table 1.1 Basic File Terminology

23. Contents of the AGENT File Figure 1.4

24. A Simple File System Figure 1.5

33. File System Critique • File System Data Management • File systems require extensive programming in a third-generation language (3GL). • As the number of files expands, system administration becomes difficult. • Making changes in existing file structures is important and difficult. • Security features to safeguard data are difficult to program and usually omitted. • Difficulty to pool data creates islands of information.

34. File System Critique • Structural and Data Dependence • Structural Dependence A change in any file’s structure requires the modification of all programs using that file. • Data Dependence A change in any file’s data characteristics requires changes in all data access programs. • Significance of data dependence is the difference between the data logical format and the data physical format. • Data dependence makes file systems extremely cumbersome from a programming and data management point of view.

35. File System Critique • Field Definitions and Naming Conventions • A good (flexible) record definition anticipates reporting requirements by breaking up fields into their components. • Example: • Customer Name  Last Name, First Name, Initial • Customer Address  Street Address, City, State

36. File System Critique • Field Definitions and Naming Conventions • Selecting proper field names is very important. • Names must be as descriptive as possible within restrictions. • Naming must reflect designer’s documentation needs and user’s reporting and processing requirements.

37. File System Critique • Data Redundancy: Uncontrolled data redundancy sets the stage for • Data Inconsistency (lack of data integrity) • Data anomalies • Modification anomalies • Insertion anomalies • Deletion anomalies

38. Figure 1.6

39. The Database System Environment Figure 1.7 Figure 1.7

40. Database Systems • The Database System Components • Hardware • Computer • Peripherals • Software • Operating systems software • DBMS software • Applications programs and utilities software

41. Database Systems • The Database System Components • People • Systems administrators • Database administrators (DBAs) • Database designers • Systems analysts and programmers • End users • Procedures • Instructions and rules that govern the design and use of the database system • Data • Collection of facts stored in the database

42. Database Systems • The Database System Components • The complexity of database systems depends on various organizational factors: • Organization’s size • Organization’s function • Organization’s corporate culture • Organizational activities and environment • Database solutions must be cost effective AND strategically effective.

43. Database Systems • Types of Database Systems • Number of Users • Single-user • Desktop database • Multiuser • Workgroup database • Enterprise database • Scope • Desktop • Workgroup • Enterprise

44. Database Systems • Types of Database Systems • Location • Centralized • Distributed • Use • Transactional (Production) • Decision support • Data warehouse