Database Environment

1
Database Environment

• Chapter 2

2
The Three-Level ANSI-SPARCArchitecture

• External Level
• Conceptual Level
• Internal Level
• Physical Data

3
External Level

• The users view of the database. This level
  describes that part of the database that is
  relevant to the user

4
Conceptual Level

• The community view of the database. This level
  describes what data is stored in the database and
  the relationships among data.
• This level represents
• All entities and their attributes and their
  relationships
• The constraints on the data
• Semantic information about the data
• Security and Integrity of Information

5
Internal Level

• This level describes the physical representation
  of the data on the computer.
• Schemas, mapping and instances
• Data Independence
• Logical data independence ( Immunity of the
  external schema to changes in the conceptual
  schema)
• Physical data independence ( Immunity of the
  conceptual schema to changes in the internal
  schema_

6
Database Languages

• The Data Definition Language
• The Data Manipulation Language
• Procedural DML
• Nonprocedural DML
• Fourth Generation Languages
• Form Generators, Report Generators, Graphics
  Generators, Application Generators

7
Data Models and Conceptual Modeling

• Data Model An Integration collection of
  concepts to describe and manipulate data
• Object-Based Data Models
• Entity-Relationship
• Semantic
• Record-Based Model
• Relational
• Network
• Hierarchical

8
Components of a DBMS

• Query processor
• Database Manager
• File Manager
• DML processor
• DDL complier
• Catalog Manager

9
Software Components of the Database Manager

• Authorization Control
• Command Processor
• Integrity Checker
• Query Optimizer
• Transaction Manager
• Schedule
• Recover Manager
• Buffer Manager

10
Multi-User DBMS Architecture

• Teleprocessing
• File-Server
• Client-Server

11
System Catalogs

• A Repository of Information describing the data
  in the database

12
Functions of a DBMS

• Storage, Retrieval and Update
• A User-accessible catalog
• Transaction Support
• Concurrency Control and Services
• Authorization Services
• Support for Data Communication
• Integrity Services
• Services to Promote Data Independence
• Utility Services