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Chapter 2 Database Environment

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1 Chapter 2 Database Environment
Thomas Connolly, Carolyn Begg, Database System, A Practical Approach to Design Implementation and Management, 4th Edition, Addison Wesley Pg 33 ~ 62

2 Learning Outcomes Three-Level ANSI-SPARC Architecture
Database Languages Data Models Functions of DBMS Components of DBMS Teleprocessing

3 ANSI/SPARC ANSI SPARC 1975 American National Standards Institute
Standards Planning and Requirements Committee 1975 Proposed a framework for DBS

4 Three-Level ANSI-SPARC Architecture
External level (Database Users) Provide a view of the database tailored to a user Data gathering Conceptual level (Database Designer) Deals with the organization of data as a whole Constraints and security Entity-relationship diagram Normalization Internal level (System Designer) Deal with physical storage of data Storage, index, compression, & encryption File organization

5 Database Schemas Database schema (intension) & database instance (extension) External schemas (subschema) Conceptual schema (database schema) Internal schema

6 Mapping Translate information from one level to the next
External/conceptual mapping Conceptual/internal mapping Provide data independence

7 Data Independence Logical data independence Physical data independence
Conceptual level changed shouldn’t affect external levels Physical data independence Change to internal level shouldn’t affect conceptual level

8 ANSI/SPARC Architecture

9 Database Languages Data Definition Language (DDL)
Structured Query Language (SQL) Data Manipulation Language (DML) Procedural DML Non-procedural DML Query-by-Example (QBE) Fourth-Generation Language Form, report, graphics, & application generators

10 Data Models Definition Types
Integrated concept for describing data, relationships and constraints Types Object-based data models Record-based data models Physical data models (internal structure, ordering, & paths)

11 Object-Based Data Models
Entity-relationship Entity, attribute, relationship Usage: documentation Object-oriented Object, class, subclass, inheritance, state (attributes), behavior (methods or actions), encapsulation, message, polymorphism Usage: building software

12 Record-Based Data Models
Relational data model Network model Hierarchical Model

13 Relational Data Model Terminology Record relationship Usage Relations
Attributes Tuples Record relationship One-to-many relationship Usage Ad hoc reporting

14 Network Model CODASYL DBTG Terminology Record relationship Usage
Data item & group item Record type: owner, member Set type: optional, mandatory, permanent Record relationship Many-to-many relationship Link or pointer between set owner and set member Usage Large volume transaction processing

15 Hierarchical Model IBM Information Management Systems Terminology
Tree, general tree, & subtree Nodes, root node, parent node, and child node Segment type ( root, parent, child) Record relationship One-to-many relationship Link or pointer between parent node and child node No many-to-many relationship Usage Large volume transaction processing

16 Functions of a DBMS Data storage, retrieval and update
A user-accessible catalog Transaction support Concurrency control Recovery Authorization Integrity Data independence Data communication Other Utilities

17 Components of a DBMS Query processor Database manager File manager
DML preprocessor DDL compiler Catalog manager

18 Components of Database Manager
Authorization control Command processor Integrity checker Query optimizer Transaction manager Scheduler Recovery manager Buffer manager

19 Teleprocessing - I Two-tier client-server architecture
Client: user interface, business and data processing logic Database server: data validation and database access Advantage Accessing to distributed database Increasing performance and consistency Lowering server and communication cost Supporting open systems architecture

20 Teleprocessing - II Three-tier client-server architecture
Client: user interface Application server: business and processing logic Database server: data validation and database access Advantage Reducing client cost Software distribution Maintenance cost Balancing load

21 Teleprocessing - III Transaction processing (TP) monitor
Transaction manager between client and server Advantage Transaction routing Distributed transaction for load balancing

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