week1 lecture2 on DataBaseManagementSystem.ppt

Distributed DBMS © 2001 M. Tamer Özsu & Patrick Valduriez Page 1.1
Outline
 Introduction
What is a distributed DBMS
Problems
Current state-of-affairs
 Background
 Distributed DBMS Architecture
 Distributed Database Design (Briefly)
 Distributed Query Processing (Briefly)
 Distributed Transaction Management (Extensive)
 Building Distributed Database Systems (RAID)
 Mobile Database Systems
 Privacy, Trust, and Authentication
 Peer to Peer Systems

File Systems
program 1
data description 1
program 2
data description 2
program 3
data description 3
File 1
File 2
File 3

Database Management
database
DBMS
Application
program 1
(with data
semantics)
Application
program 2
(with data
semantics)
Application
program 3
(with data
semantics)
description
manipulation
control

Integrate Databases and Commuinication
Database
Technology
Computer
Networks
integration distribution
integration
Distributed
Database
Systems

Distributed Computing
 A number of autonomous processing elements (not
necessarily homogeneous) that are interconnected by a
computer network and that cooperate in performing their
assigned tasks.

 Synonymous terms
distributed data processing
multiprocessors/multicomputers
satellite processing
backend processing
dedicated/special purpose computers
timeshared systems
functionally modular systems
Peer to Peer Systems
Distributed Computing

 Processing logic
 Functions
 Data
 Control
What is distributed …

What is a Distributed Database System?
A distributed database (DDB) is a collection of multiple, logically
interrelated databases distributed over a computer network.
A distributed database management system (D–DBMS) is the
software that manages the DDB and provides an access
mechanism that makes this distribution transparent to the users.
Distributed database system (DDBS) = DB + Communication

 A timesharing computer system
 A loosely or tightly coupled multiprocessor system
 A database system which resides at one of the nodes of a
network of computers - this is a centralized database on a
network node
What is not a DDBS?

Centralized DBMS on a Network
Site 5
Site 1
Site 2
Site 3
Site 4
Communication
Network

Distributed DBMS Environment
Site 5
Site 1
Site 2
Site 3
Site 4
Communication
Network

Implicit Assumptions
 Data stored at a number of sites  each site logically
consists of a single processor.
 Processors at different sites are interconnected by a
computer network  no multiprocessors
parallel database systems
 Distributed database is a database, not a collection of
files  data logically related as exhibited in the users’
access patterns
relational data model
 D-DBMS is a full-fledged DBMS
not remote file system, not a TP system

Shared-Memory Architecture
Examples : symmetric multiprocessors (Sequent, Encore)
and some mainframes (IBM3090, Bull's
DPS8)
P1 Pn M
D

Shared-Nothing Architecture
Examples : Teradata's DBC, Tandem, Intel's Paragon,
NCR's 3600 and 3700
P1
M1
D1
Pn
Mn
Dn

 Manufacturing - especially multi-plant manufacturing
 Military command and control
 Electronic fund transfers and electronic trading
 Corporate MIS
 Airline restrictions
 Hotel chains
 Any organization which has a decentralized
organization structure
Applications

 Transparent management of distributed, fragmented,
and replicated data
 Improved reliability/availability through distributed
transactions
 Improved performance
 Easier and more economical system expansion
Distributed DBMS Promises

Transparency
 Transparency is the separation of the higher level semantics of a
system from the lower level implementation issues.
 Fundamental issue is to provide
data independence
in the distributed environment
 Network (distribution) transparency
 Replication transparency
 Fragmentation transparency
 horizontal fragmentation: selection
 vertical fragmentation: projection
 hybrid

Example
TITLE SAL
PAY
Elect. Eng. 40000
Syst. Anal. 34000
Mech. Eng. 27000
Programmer 24000
PROJ
PNO PNAME BUDGET
ENO ENAME TITLE
E1 J. Doe Elect. Eng.
E2 M. Smith Syst. Anal.
E3 A. Lee Mech. Eng.
E4 J. Miller Programmer
E5 B. Casey Syst. Anal.
E6 L. Chu Elect. Eng.
E7 R. Davis Mech. Eng.
E8 J. Jones Syst. Anal.
EMP
ENO PNO RESP
E1 P1 Manager 12
DUR
E2 P1 Analyst 24
E2 P2 Analyst 6
E3 P3 Consultant 10
E3 P4 Engineer 48
E4 P2 Programmer 18
E5 P2 Manager 24
E6 P4 Manager 48
E7 P3 Engineer 36
E8 P3 Manager 40
ASG
P1 Instrumentation 150000
P3 CAD/CAM 250000
P2 Database Develop. 135000
P4 Maintenance 310000
E7 P5 Engineer 23

Transparent Access
SELECT ENAME,SAL
FROM EMP,ASG,PAY
WHERE DUR > 12
AND EMP.ENO = ASG.ENO
AND PAY.TITLE = EMP.TITLE Paris projects
Paris employees
Paris assignments
Boston employees
Montreal projects
Paris projects
New York projects
with budget > 200000
Montreal employees
Montreal assignments
Boston
Communication
Network
Montreal
Paris
New
York
Boston projects
Boston employees
Boston assignments
Boston projects
New York employees
New York projects
New York assignments
Tokyo

week1 lecture2 on DataBaseManagementSystem.ppt

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