Distributed Database Management Systems (a) 1 (MO3, Chapter 12-1 to 12-6) + page 537

Question 1

What is a distributed database system

Answer 1

• Governs storage and processing of logically related data
  over interconnected computer systems;
• Distributes data and processing functions among several
  sites

Question 2

Centralized database management system:

Answer 2

Required corporate data be stored in a single central site;
* Provided data access through dumb terminals;
* Filled structured information needs of corporations; fell short
when quickly moving events required faster response times
and equally quick access to information

Question 3

What are two new database requirements

Answer 3

Rapid ad hoc data access
distributed data access

Question 4

Changes that affected the nature of systems

Answer 4

Globalization of business operation;
* Increased market needs for an on-demand transaction style,
based on web-based services;
* Rapid social and technological changes fueled by low-cost
smart mobile devices;
* Converging data realms in the digital world;
* Advent of social media to reach new customers and
markets.

Question 5

What are the factors that influenced ddbms

Answer 5

Acceptance of Internet as a platform for business;
* Mobile wireless revolution;
* Growth of use of “application as a service”;
* Focus on mobile business intelligence;
* Emphasis on Big Data analytics.

Question 6

Potential centralized DBMS problems:

Answer 6

• Performance degradation;
• High costs;
• Reliability problems;
• Scalability problems;
• Organizational rigidity

Question 7

DDBMS Advantages and
Disadvantages

Answer 7

Advantages:
Data is located near the site of the greatest demand
Faster data access
Faster data processing
Growth facilitation
Improved communications
Reduced operating costs
USer friendly interface
Less danger of a single point failure
Processor independence
Disadvantages
Complexity of management and control
Technological difficulty
Secuirty
Lack of standards
Increaed storage and iunfrastructure requirements
increaed training costs
higher costs

Question 8

• Distributed processing:

Answer 8

database’s logical processing is shared
among two or more physically independent sites via network

Question 9

• Distributed database:

Answer 9

stores logically related database over
two or more physically independent sites via a computer
network.

Question 10

• Database fragments:

Answer 10

database composed of many parts in
distributed database system.

Question 11

Characteristics of Distributed
Management Systems

Answer 11

A DBMS must have several functions to be classified as
distributed:
* Application interface;
* Validation;
* Transformation;
* Query optimization;
* Mapping;
* I/O interface;
* Formatting;
* Security;
* Backup and recovery;
* DB administration;
* Concurrency control;
* Transaction management.

Question 12

Functions of fully distributed DBMS

Answer 12

Receive the request of an application or end user;
* Validate, analyze, and decompose the request;
* Map request’s logical-to-physical data components;
* Decompose request into several I/O operations;
* Search, locate, read and validate data;
* Ensure database consistency, security, and integrity;
* Validate data for conditions specified by request;
* Present data in required format;
* Handle all necessary functions transparently to user

Question 13

Components of a distributed database system

Answer 13

Computer workstations or remote devices
Network hardware and software components
Communications media
Transaction processor
Data processor

Question 14

Transaction processor

Answer 14

Software component found in each computer or device that requests data

Question 15

Data processor

Answer 15

Software component residing on each computer or device that stores and retrieves data located at the site

Question 16

Levels of Data and Process
Distribution

Answer 16

Single site process
Multiple site process

Question 17

Single site process

Answer 17

• Characteristics:
• Processing is done on a single host computer;
• Data stored on host computer’s local disk;
• Processing cannot be done on end user’s side;
• DBMS is accessed by connected terminals.

Question 18

Multiple-Site Processing, Single-Site
Data (MPSD

Answer 18

• Multiple processes run on different computers sharing a single
  data repository.
• Typically requires network file server running conventional
  applications.
• Accessed through LAN.
• Client/server architecture:
• Reduces network traffic;
• Distributes processing;
• Supports data at multiple sites

Question 19

Multiple-Site Processing, Multiple-Site
Data (MPMD)

Answer 19

• Fully distributed database management system
• Support multiple data processors and transaction processors
  at multiple sites.

Question 20

Classifications:

Answer 20

• Homogeneous: integrate multiple instances of same DBMS
  over a network.
• Heterogeneous: integrate different types of DBMSs over a
  network.
• Fully heterogeneous: support different DBMSs, each
  supporting different data model running under different
  computer systems.

Question 21

Multiple-Site Processing, Multiple-Site
Data (MPMD)Restrictions of DDBMS:

Answer 21

• Remote access is provided on a read-only basis;
• Restrictions on the number of remote tables that may be
  accessed in a single transaction;
• Restrictions on the number of distinct databases that may be
  accessed;
• Restrictions on the database model that may be accessed.