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

1 1 Introducing the Database 4Major Database Concepts u Data and information l Data - Raw facts l Information - Processed data u Data management u Database u Metadata u Database management system (DBMS)

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1 1 Figure 1.1 Sales per Employee for Each of ROBCOR’S Two Divisions

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1 1 Introducing the Database 4Importance of DBMS u It helps make data management more efficient and effective. u Its query language allows quick answers to ad hoc queries. u It provides end users better access to more and better-managed data. u It promotes an integrated view of organization’s operations -- “big picture.” u It reduces the probability of inconsistent data.

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1 1 Figure 1.2 The DBMS Manages the Interaction Between the End User and the Database

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1 1 Introducing the Database 4Why Database Design Is Important? u A well-designed database facilitates data management and becomes a valuable information generator. u A poorly designed database is a breeding ground for uncontrolled data redundancies. u A poorly designed database generates errors that lead to bad decisions.

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1 1 Historical Roots 4Why Study File Systems? u It provides historical perspective. u It teaches lessons to avoid pitfalls of data management. u Its simple characteristics facilitate understanding of the design complexity of a database. u It provides useful knowledge for converting a file system to a database system.

1 1 Figure 1.3 Contents of the CUSTOMER File

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1 1 Table 1.1 Basic File Terminology

1 1 Figure 1.4 Contents of the AGENT File

1 1 A Simple File System Figure 1.5

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1 1 File System Critique 4File System Data Management u File systems require extensive programming in a third-generation language (3GL). u As the number of files expands, system administration becomes difficult. u Making changes in existing file structures is important and difficult. u Security features to safeguard data are difficult to program and usually omitted. u Difficulty to pool data creates islands of information.

1 1 File System Critique 4Structural and Data Dependence u Structural Dependence A change in any file’s structure requires the modification of all programs using that file. u Data Dependence A change in any file’s data characteristics requires changes in all data access programs. u Significance of data dependence is the difference between the data logical format and the data physical format. u Data dependence makes file systems extremely cumbersome from a programming and data management point of view.

1 1 File System Critique 4Field Definitions and Naming Conventions u A good (flexible) record definition anticipates reporting requirements by breaking up fields into their components. l Example: –Customer Name  Last Name, First Name, Initial –Customer Address  Street Address, City, State

1 1 File System Critique 4Field Definitions and Naming Conventions u Selecting proper field names is very important. l Names must be as descriptive as possible within restrictions. l Naming must reflect designer’s documentation needs and user’s reporting and processing requirements.

1 1 File System Critique 4Data Redundancy: Uncontrolled data redundancy sets the stage for u Data Inconsistency (lack of data integrity) u Data anomalies l Modification anomalies l Insertion anomalies l Deletion anomalies

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1 1 Figure 1.7 The Database System Environment Figure 1.7

1 1 Database Systems 4The Database System Components u Hardware l Computer l Peripherals u Software l Operating systems software l DBMS software l Applications programs and utilities software

1 1 Database Systems 4The Database System Components u People l Systems administrators l Database administrators (DBAs) l Database designers l Systems analysts and programmers l End users u Procedures l Instructions and rules that govern the design and use of the database system u Data l Collection of facts stored in the database

1 1 Database Systems 4The Database System Components u The complexity of database systems depends on various organizational factors: l Organization’s size l Organization’s function l Organization’s corporate culture l Organizational activities and environment u Database solutions must be cost effective AND strategically effective.

1 1 Database Systems 4Types of Database Systems u Number of Users l Single-user –Desktop database l Multiuser –Workgroup database –Enterprise database u Scope l Desktop l Workgroup l Enterprise

1 1 Database Systems 4Types of Database Systems u Location l Centralized l Distributed u Use l Transactional (Production) l Decision support l Data warehouse

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