Intro

1
Intro Part 2

• Introduction to Database Management Ch 1 2

2
Important Points

• DBMS Functions
• DBMS Architectures
• Database Development Phases

3
Functions of a DBMS

• Eight services that a DBMS should provide
  (Codd82)
• 1) Data storage, retrieval, and update
• 2) A user-accessible catalog describing data
  items
• 3) Transaction support
• 4) Concurrency control services
• 5) Recovery services
• 6) Authorization (security) services
• 7) Support for data communication (network
  access)
• 8) Data integrity services

4
Database System Approach
5
Components of a DBMS

• A DBMS is a complicated software system
  containing many components
• Query processor - translates user/application
  queries into low-level data manipulation actions.
• Sub-components query parser, query optimizer
• Storage manager - maintains storage information
  including memory allocation, buffer management,
  and file storage.
• Sub-components buffer manager, file manager
• Transaction manager - performs scheduling of
  operations and implements concurrency control
  algorithms.
• Access manager controls access to a database

6
Overall System Structure
7
Database Architectures

• There are several different database
  architectures
• File-server architecture - files are shared but
  DBMS processing occurs at the clients (e.g.
  Microsoft Access)
• Two-Tier client-server architecture - dedicated
  machine running DBMS accessed by clients (e.g.
  SQL Server, MySQL)
• Three-Tier client-server architecture - DBMS is
  bottom tier, second tier is an application server
  containing business logic, top tier is clients
  (e.g. Web browser/Web Server/PHP/MySQL)

8
Two-Tier Client-Server Architecture

• Advantages
• Only one copy of DBMS software on dedicated
  machine.
• Increased performance.
• Reduced hardware and communication costs.
• Easier to maintain consistency and manage
  concurrency.

9
Three-Tier Client-Server Architecture

• Advantages
• Reduced client administration and cost using thin
  web clients.
• Easy to scale architecture and perform load
  balancing.

10
Database Development Phases
11
Conceptual Data Modeling

• Information content of the database
• Entity relationship diagram (ERD) showing entity
  types and relationships
• Diverse formats for database requirements

12
Logical Database Design

• Refine conceptual design
• Convert ERD to table design
• Normalization tool to reason about redundancies
• Add constraints to enforce business rules

13
Physical Database Design

• Performed at each independent database site
• Minimize response time without consuming
  excessive resources
• Tradeoffs retrieval versus update
• Flexible designs versus specialized designs
• Decisions indexes, data placement