Distributed Database Management Systems: Lecture 11

Distributed Database Management Systems: Lecture 11. The main topics covered in this chapter include: major DDBS architectures; client-server architecture; one server multiple clients; server performs most of the data management; query processing; transaction and storage management; peer-to-peer distributed systems;...

Distributed Database Management System

Lecture 10

Major DDBS Architectures

Client-Server Architecture

• Basic idea is to distribute

functionality

• Gives two level architecture

• The term used in different

meanings; generally C and S refer

to processes, may be running at

the same machines

– As you can see in the figure

Management;

• Query Processing

• Transaction and Storage Management

• application and user interface

• a client module of DBMS

• Data and lock management cached their

sometimes

running at both

• Client passes user queries to

server without trying to

understand or optimize them

• One Server Multiple Clients

• Multiple Servers

time

Peer-to-Peer Distributed Systems

LIS1 LIS2 LISn

GCS

ES1

• Physical data organization at

each site defining Local Internal

Schemas

• On top of that, Local Conceptual

Schema

• Then the overall view is depicted

by Global conceptual schema that supports the External schemas

• Transparencies Supported

• Extension of ANSI/SPARC Model

• Data Independence supported

• Local Data Dictionary and global

exist

• Both support local and global

mappings

Interpreting user commands  and formats results

Checks if user query can be  processed

Optimized execution strategy Global queries to local ones Coordinates distribution  execution of user requests

Chooses best access path to  any data item

Makes sure the consistency of  local data even in case of 

failure

Physically accesses the data as  per the commands generated 

A Multidatabase System

autonomous heterogeneous, and distributed databases Two Major architectures:

• Global Schema Architecture

• Federated Schema Architecture

Major DDBS Architectures-III

 L External

Schema

 G External Schema

Global Schema

Component

Schema Integration

 G External Schema

 L External Schema