2. 11 Interacting with Databases Through the Web 8
3. 12 Database Administration & Security 15
4. 13 Managing Transactions and Concurrency 33
5. 14 Managing Database and SQL Performance 38
6. 15 Databases for Decision Support 43
Database Principles: Fundamentals of Design, Implementation, and Management
10th Edition - Coronel C, Morris S, Rob P.
v1.00 September 2013
Ron Barnard
,Chapter 10 - Distributed Databases
Chapter 10 - Distributed Databases
Question 1
Describe the evolution from centralized DBMSs to distributed DBMSs.
n/a
Question 2
List and discuss some of the factors that influenced the evolution of the DDBMS.
• Business operations became global, competition changed from local to Web store in cyberspace;
• Customer demands and market needs favoured on-demand transaction style;
• Technological changes - mobile smart devices increased demand for complex and fast networks;
• Multiple types of data, geographically dispersed;
(Ref: Ch 10.1 page 443)
Question 3 [May / June 2011] [May / Jun 2012]
What are the advantages of the DDBMS ?
• Data are located near the site of greatest demand - data dispersed to match business requirements
• Faster data access - work with nearest stored data subset;
• Faster data processing - data processed at several sites;
• Growth facilitation - new sites can be added without affecting existing sites;
• Improved communications - local sites are smaller and located closer to customers;
• Reduced operating costs - more cost effective to add nodes to a network than upgrade mainframe;
• User-friendly interface - PCs equipped with easy to use GUI;
• Less danger of single-point failure - if one computer fails, workload picked up by other computers;
• Processor independence - user can access any available copy of data, processed by any
processor at the data location.
(Ref: Ch 10.2 page 445)
Question 4 [May / June 2011] [May / Jun 2012]
What are the disadvantages of the DDBMS ?
• Complexity of management and control - working with data at various locations;
• Technological difficulty - more technical issues to deal with;
• Security - probability of security lapses increases when data are stored at multiple sites;
Page 2 of 51
, Chapter 10 - Distributed Databases
• Lack of standards - no standard communication protocols;
• Increased storage and infrastructure requirements - multiple copies of data at multiple sites;
• Increased training cost - higher than compared to a centralized model;
• Costs - require duplicated infrastructure.
(Ref: Ch 10.2 page 445)
Question 5
Explain the difference between a distributed database and distributed processing.
Distributed database - stores logically related database over two or more physically independent sites,
connected via a network.
Distributed processing - a databases' logical processing is shared among two or more physically
independent sites that are connected through a network. The database is located on one computer, but
several sites can access the data and update the database.
(Ref: Ch 10.3 page 446)
Question 6 [May / Jun 2013]
What is a fully distributed database management system ?
Must perform all of the functions of a centralized DBMS -
• Receive the request of an application or end user;
• Validate, analyze, and decompose the request;
• Map the requests' logical-to-physical data components;
• Decompose the request into several disk I/O operations;
• Search for, locate, read, and validate the data;
• Ensure database consistency, security, and integrity;
• Validate the data for the conditions, if any, specified by the request;
• Present the selected data in the required format.
(Ref: Ch 10.4 page 448)
Question 7
What are the components of a DDBMS ?
• Computer workstations or remote devices;
• Network hardware and software;
• Communications media, that carry the data from one node to another;
• Transaction Processor - software component in each computer that requests data;
• Data Processor - software component on each computer that stores and retrieves data located at
that site.
(Ref: Ch 10.5 page 449)
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