Database Architecture Introduction to Databases The Nature of

Database Architecture Introduction to Databases

The Nature of Data • Un-structured • Semi-structured • Structured

Semantic Hierarchy of Data Models High Semantics Object-Oriented Object-Relational 3 rd Generation 2 nd Generation Network Hierarchical Low Semantics File-Based Systems 1 st Generation

File-Based System Limitations • • • Separation and Isolation of Data Duplication of Data Dependence Incompatible File Formats Issues with Data Security, Proliferation of Application Programs • Data Management

The Database Management System (DBMS)…. what is it? A software system that enables users to define, create, maintain, and control access to the database.

Advantages of a Database Management System • • • Views Control of data redundancy Data consistency Sharing of data Improved data integrity Improved security Enforcement of Standards Increased Productivity Improved Maintenance through data independence Increased Concurrency

Disadvantages of a Database Management System (DBMS) • • Complexity Cost Higher Impact of Failures Support Requirements

Database Layers of Abstraction Three Level ANSI-SPARC Architecture View Layer Architecture Logical Layer Architecture Physical Layer Architecture

Database Languages Structure Query Language (SQL) Data Definition Language Data Manipulation Language Data Control Language SELECT (Query Language) Data Manipulation Language

Data and Meta-data Database DATA META-DATA

Functions of the DBMS • • • Data storage, retrieval, and update A user-accessible catalog (meta-data) Transaction Support Concurrency Control Recovery Services Authorization Services Support for Data Communication Integrity Services Data Independence Services Utilities

Components of the DBMS 1. Schema Modification 2. Data Modification 3. Query 3 Possible Inputs Query Processing Transaction Management Storage Management Database

Database Systems The DBMS resides in server memory The physical database resides on disk