Download Week 1 Lecture 2

Outline

Introduction
 What is a distributed DBMS
 Problems
 Current state-of-affairs
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Distributed DBMS
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
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.1
File Systems
program 1
data description 1
File 1
program 2
data description 2
File 2
program 3
data description 3
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
File 3
Page 1.2
Database Management
Application
program 1
(with data
semantics)
Application
program 2
(with data
semantics)
DBMS
description
manipulation
control
database
Application
program 3
(with data
semantics)
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.3
Integrate Databases and
Commuinication
Database
Technology
Computer
Networks
integration
distribution
Distributed
Database
Systems
integration
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.4
Distributed Computing
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A number of autonomous processing elements
(not necessarily homogeneous) that are
interconnected by a computer network and that
cooperate in performing their assigned tasks.
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.5
Distributed Computing
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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 DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.6
What is distributed …
Distributed DBMS
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Processing logic
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Functions
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Data
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Control
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.7
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
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.8
What is not a DDBS?
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A timesharing computer system
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A loosely or tightly coupled multiprocessor
system
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A database system which resides at one of the
nodes of a network of computers - this is a
centralized database on a network node
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.9
Centralized DBMS on a Network
Site 1
Site 2
Site 5
Communication
Network
Site 4
Distributed DBMS
Site 3
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.10
Distributed DBMS Environment
Site 1
Site 2
Site 5
Communication
Network
Site 4
Distributed DBMS
Site 3
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.11
Implicit Assumptions
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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
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Distributed database is a database, not a
collection of files  data logically related as
exhibited in the users’ access patterns
 relational data model
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D-DBMS is a full-fledged DBMS
 not remote file system, not a TP system
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.12
Shared-Memory Architecture
P1
Pn
M
D
Examples : symmetric multiprocessors (Sequent,
Encore) and some mainframes
(IBM3090, Bull's DPS8)
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.13
Shared-Nothing Architecture
P1
M1
D1
Pn
Dn
Mn
Examples : Teradata's DBC, Tandem, Intel's
Paragon, NCR's 3600 and 3700
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.14
Applications
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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
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.15
Distributed DBMS Promises
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Transparent management of distributed,
fragmented, and replicated data
Improved reliability/availability through
distributed transactions
Improved performance
Easier and more economical system
expansion
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.16
Transparency
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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
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Page 1.17
Example
ASG
EMP
ENO
ENAME
TITLE
E1
E2
E3
E4
E5
E6
E7
E8
J. Doe
M. Smith
A. Lee
J. Miller
B. Casey
L. Chu
R. Davis
J. Jones
Elect. Eng.
Syst. Anal.
Mech. Eng.
Programmer
Syst. Anal.
Elect. Eng.
Mech. Eng.
Syst. Anal.
ENO PNO
PROJ
Distributed DBMS
E1
E2
E2
E3
E3
E4
E5
E6
E7
E7
E8
P1
P1
P2
P3
P4
P2
P2
P4
P3
P5
P3
RESP
Manager
Analyst
Analyst
Consultant
Engineer
Programmer
Manager
Manager
Engineer
Engineer
Manager
DUR
12
24
6
10
48
18
24
48
36
23
40
PAY
PNO
PNAME
BUDGET
TITLE
SAL
P1
P2
P3
P4
Instrumentation
Database Develop.
CAD/CAM
Maintenance
150000
135000
250000
310000
Elect. Eng.
Syst. Anal.
Mech. Eng.
Programmer
40000
34000
27000
24000
© 2001 M. Tamer Özsu & Patrick Valduriez
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Transparent Access
SELECT
FROM
WHERE
AND
AND
ENAME,SAL
EMP,ASG,PAY
DUR > 12
EMP.ENO = ASG.ENO
PAY.TITLE = EMP.TITLE
Tokyo
Paris
Boston
Communication
Network
Paris projects
Paris employees
Paris assignments
Boston employees
Boston projects
Boston employees
Boston assignments
Montreal
New
York
Boston projects
New York employees
New York projects
New York assignments
Distributed DBMS
© 2001 M. Tamer Özsu & Patrick Valduriez
Montreal projects
Paris projects
New York projects
with budget > 200000
Montreal employees
Montreal assignments
Page 1.19