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Chapter 01. Introduction to Distributed Database. Overview. File System Menyediakan suatu prosedur bagi suatu program untuk menyimpan, melakukan update, dan mengambil data pada suatu media penyimpanan atau storage. Overview. Database Management System

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Chapter 01

Chapter 01

Introduction to Distributed Database


Overview

Overview

  • File System

    • Menyediakan suatu prosedur bagi suatu program untuk menyimpan, melakukan update, dan mengambil data pada suatu media penyimpanan atau storage


Overview1

Overview

  • Database Management System

    • Suatu paket software yang melakukan kontrol, dan pengelolaan data di dalam database (kumpulan data)


Db clients servers and environments

DB Clients, Servers, and Environments

  • DB-Server, a collection of programs that execute all DBMS function

  • DB-Client, any application program that needs to connect to a DB-Server

  • DB Environment (DBE), one or more DBs along with any software providing at least minimum set of required data operation and management.


Dbe architectural concept

DBE Architectural concept

  • Service, logical collections of related functionality. Example: Query Service

  • Sites, represents a logical location in an architectural diagram or deployment diagram

  • Component and Subsystem (COS)

    • Component, Deployable bundle of software that provide reasonability cohesive set of functionality

    • Subsystem, collection of one or more components that work together toward a common goal


Dbe architectures

DBE Architectures

  • Required Services

    • Data Read Service (Drd-S)

    • Security Service (Sec-S)

    • Semantic Integrity Service (Semi-S)


Dbe architectures1

DBE Architectures

  • Basic Services

    • Data Read Service (Drd-S)

    • Security Service (Sec-S)

    • Semantic Integrity Service (Semi-S)

    • Data Write Service (Dwr-S)


Dbe architectures2

DBE Architectures

  • Expected Service

    • Data Read Service (Drd-S)

    • Security Service (Sec-S)

    • Semantic Integrity Service (Semi-S)

    • Data Write Service (Dwr-S)

    • Query Request Service (Qreq-S)

    • Query Optimization Service

    • Execution Service

    • Execution Optimization Service


Dbe architectures3

DBE Architectures

  • Expected Subsystem

    • Data Read Service (Drd-S)

    • Security Service (Sec-S)

    • Semantic Integrity Service (Semi-S)

    • Data Write Service (Dwr-S)

    • Query Request Service (Qreq-S)

    • Query Optimization Service

    • Execution Service

    • Execution Optimization Service

    • User Interface


Dbe architectures4

DBE Architectures

  • Typical DBMS Service

    • Drd-S, Sec-S, Semi-S, Dwr-S, Qreq-S

    • Query Optimization Service

    • Execution Service

    • Execution Optimization Service

    • User Interface

    • Transaction Management (Trans-S)

    • Locking Service (Lock-S)

    • Timestamping Service (Times-S)

    • Deadlock Handling Service

    • Fallback and Recovery Service


Motivation

Motivation

Database

Technology

Computer

Networks

integration

distribution

Distributed

Database

Systems

integration

integration ≠ centralization


Dbms schema architecture

DBMS Schema Architecture


Ddbms schema architecture

DDBMS Schema Architecture


Top down ddbms software architecture

Top Down DDBMS Software Architecture


Bottom up ddbms software architecture

Bottom Up DDBMS Software Architecture


Generic ddbms architecture

Generic DDBMS architecture


Distributed computing

Distributed Computing

  • A concept in search of a definition and a name.

  • 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 computing1

Distributed Computing

  • Synonymous terms

    • distributed function

    • distributed data processing

    • multiprocessors/multicomputers

    • satellite processing

    • backend processing

    • dedicated/special purpose computers

    • timeshared systems

    • functionally modular systems


What is distributed

What is distributed …

  • Processing logic

  • Functions

  • Data

  • Control


What is a distributed database system

What is a Distributed Database System?

A distributed database (DDB) is a collection of multiple, logically interrelateddatabases 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) = DDB + D–DBMS


What is not a ddbs

What is not a DDBS?

  • 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


Centralized dbms on a network

Centralized DBMS on a Network

Site 1

Site 2

Site 5

Communication

Network

Site 4

Site 3


Distributed dbms environment

Distributed DBMS Environment

Site 1

Site 2

Site 5

Communication

Network

Site 4

Site 3


Implicit assumptions

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

D

Shared-Memory Architecture

Examples :symmetric multiprocessors (Sequent, Encore) and some mainframes (IBM3090, Bull's DPS8)

P1

Pn

M


Shared disk architecture

P1

M1

Shared-Disk Architecture

Pn

D

Mn

Examples :DEC's VAXcluster, IBM's IMS/VS Data Sharing


Shared nothing architecture

P1

D1

M1

Shared-Nothing Architecture

Examples :Teradata's DBC, Tandem, Intel's Paragon, NCR's 3600 and 3700

Pn

Dn

Mn


Applications

Applications

  • Manufacturing - especially multi-plant manufacturing

  • Military command and control

  • EFT

  • Corporate MIS

  • Airlines

  • Hotel chains

  • Any organization which has a decentralized organization structure


Distributed dbms promises

Distributed DBMS Promises

  • Transparent management of distributed, fragmented, and replicated data

  • Improved reliability/availability through distributed transactions

  • Improved performance

  • Easier and more economical system expansion


Transparency

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

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.

150000

Instrumentation

P1

40000

Elect. Eng.

P2

Database Develop.

135000

Syst. Anal.

34000

P3

CAD/CAM

250000

27000

Mech. Eng.

P4

Maintenance

310000

Example

ASG

EMP

ENO

ENAME

TITLE

ENO

PNO

RESP

DUR

E1

P1

Manager

12

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

E7

P5

Engineer

23

E8

P3

Manager

40

PROJ

PAY

PNAME

PNO

BUDGET

TITLE

SAL

Programmer

24000


Transparent access

Tokyo

Paris

Boston

Paris projects

Paris employees

Paris assignments

Boston employees

Communication

Network

Boston projects

Boston employees

Boston assignments

Montreal

New

York

Montreal projects

Paris projects

New York projects

with budget > 200000

Montreal employees

Montreal assignments

Boston projects

New York employees

New York projects

New York assignments

Transparent Access

SELECTENAME,SAL

FROMEMP,ASG,PAY

WHEREDUR > 12

ANDEMP.ENO = ASG.ENO

ANDPAY.TITLE = EMP.TITLE


Distributed database user view

Distributed Database - User View

Distributed Database


Distributed dbms reality

Distributed DBMS - Reality

User

Query

DBMS

Software

User

Application

DBMS

Software

DBMS

Software

Communication

Subsystem

User

Application

DBMS

Software

User

Query

DBMS

Software

User

Query


Potentially improved performance

Potentially Improved Performance

  • Proximity of data to its points of use

    • Requires some support for fragmentation and replication

  • Parallelism in execution

    • Inter-query parallelism

    • Intra-query parallelism


Parallelism requirements

Parallelism Requirements

  • Have as much of the data required by each application at the site where the application executes

    • Full replication

  • How about updates?

    • Updates to replicated data requires implementation of distributed concurrency control and commit protocols


System expansion

System Expansion

  • Issue is database scaling

  • Emergence of microprocessor and workstation technologies

    • Demise of Grosh's law

    • Client-server model of computing

  • Data communication cost vs telecommunication cost


Distributed dbms issues

Distributed DBMS Issues

  • Distributed Database Design

    • how to distribute the database

    • replicated & non-replicated database distribution

    • a related problem in directory management

  • Query Processing

    • convert user transactions to data manipulation instructions

    • optimization problem

    • min{cost = data transmission + local processing}

    • general formulation is NP-hard


Distributed dbms issues1

Distributed DBMS Issues

  • Concurrency Control

    • synchronization of concurrent accesses

    • consistency and isolation of transactions' effects

    • deadlock management

  • Reliability

    • how to make the system resilient to failures

    • atomicity and durability


Relationship between issues

Relationship Between Issues

Directory

Management

Query

Processing

Distribution

Design

Reliability

Concurrency

Control

Deadlock

Management


Related issues

Related Issues

  • Operating System Support

    • operating system with proper support for database operations

    • dichotomy between general purpose processing requirements and database processing requirements

  • Open Systems and Interoperability

    • Distributed Multidatabase Systems

    • More probable scenario

    • Parallel issues


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