Database development life cycle ppt

Database Systems Design, Implementation, and Management

Coronel | Morris

11e

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Chapter 9

Database Design

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Learning Objectives

In this chapter, you will learn:
That successful database design must reflect the information system of which the database is a part
That successful information systems are developed within a framework known as the Systems Development Life Cycle (SDLC)
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Learning Objectives

In this chapter, you will learn:
That within the information system, the most successful databases are subject to frequent evaluation and revision within a framework known as the Database Life Cycle (DBLC)
How to conduct evaluation and revision within the SDLC and DBLC frameworks
About database design strategies: top-down vs. bottom-up design and centralized vs. decentralized design
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The Information System

Provides for data collection, storage, and retrieval
Composed of:
People, hardware, software
Database(s), application programs, procedures
Systems analysis: Process that establishes need for and extent of information system
Systems development: Process of creating information system
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Performance Factors of an Information System

Database design and implementation
Application design and implementation
Administrative procedures
Database development: Process of database design and its implementation
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Systems Development Life Cycle (SDLC)

Traces history of an information system
Provides a picture within which database design and application development are mapped out and evaluated
Iterative rather than sequential process
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Figure 9.2 - The Systems Development Life Cycle (SDLC)

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Computer-Aided Systems Engineering (CASE)

Tool that produces:
Time and cost effective systems
Structured, documented, and standardized applications
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Figure 9.3 - The Database Life Cycle (DBLC)

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Purpose of Database Initial Study

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Figure 9.4 - A Summary of Activities in the Database Initial Study

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Database Design

Supports company’s operations and objectives
Checks the ultimate final product from all perspectives
Pointers for examining completion procedures
Data component is an element of whole system
System analysts/programmers design procedures to convert data into information
Database design is an iterative process
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Figure 9.5 - Two Views of Data: Business Manager and Database Designer

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Database Design Process

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Implementation and Loading

Install the DBMS
Virtualization: Creates logical representations of computing resources independent of underlying physical computing resources
Create the databases
Requires the creation of special storage-related constructs to house the end-user tables
Load or convert the data
Requires aggregating data from multiple sources
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Testing Factors

Physical security
Password security
Access rights
Audit trails
Data encryption
Diskless workstations
Optimization
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Levels of Database Backups

Full backup/dump: All database objects are backed up in their entirety
Differential backup: Only modified/updated objects since last full backup are backed up
Transaction log backup: Only the transaction log operations that are not reflected in a previous backup are backed up
Backups are provided with high security
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Sources of Database Failure

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Periodic Maintenance Activities

Preventive maintenance (backup)
Corrective maintenance (recovery)
Adaptive maintenance
Assignment of access permissions and their maintenance for new and old users
Generation of database access statistics
Periodic security audits
Periodic system-usage summaries
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Figure 9.8 - Parallel Activities in the DBLC and the SDLC

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Conceptual Design

Designs a database independent of database software and physical details
Conceptual data model - Describes main data entities, attributes, relationships, and constrains
Designed as software and hardware independent
Minimum data rule: All that is needed is there, and all that is there is needed
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Table 9.2 - Conceptual Design Steps

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Description of Operations

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Table 9.3 - Developing the Conceptual Model Using ER Diagrams

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Figure 9.10 - ER Modeling is an Iterative Process Based on Many Activities
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Figure 9.11 - Conceptual Design Tools and Information Sources

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Data Model Verification

Verified against proposed system processes
Revision of original design
Careful reevaluation of entities
Detailed examination of attributes describing entities
Module: Information system component that handles specific business function
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Table 9.5 - The ER Model Verification Process

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Figure 9.12 - Iterative ER Model Verification Process

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Cohesivity and Module Coupling

Cohesivity: Strength of the relationships among the module’s entities
Module coupling: Extent to which modules are independent to one another
Low coupling decreases unnecessary intermodule dependencies
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Distributed Database Design

Portions of database may reside in different physical locations
Database fragment: Subset of a database stored at a given location
Ensures database integrity, security, and performance
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Factors Affecting Software Purchasing Decision

Cost
DBMS features and tools
Underlying model
Portability
DBMS hardware requirements
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Logical and Physical Design

Logical design: Designs an enterprise-wide database that is based on a specific data model but independent of physical-level details
Validates logical model:
Using normalization
Integrity constraints
Against user requirements
Physical design: Process of data storage organization and data access characteristics of the database
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Table 9.6 - Logical Design Steps

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Table 9.7 - Mapping the Conceptual Model to the Relational Model

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Table 9.8 - Physical Design Steps

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Clustered Tables

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Database Role

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Figure 9.14 - Top-down vs. Bottom-up Design Sequencing

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Figure 9.15 - Centralized Design

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Figure 9.16 - Decentralized Design

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Figure 9.17 - Summary of Aggregation Problems

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