Databases Reference
In-Depth Information
Distributed directory management
File server approach
Fragmentation
Gateway computer
Local area network (LAN)
Local autonomy
Location transparency
Partitioning
Replicated data
Server
Three-tiered client/server approach
Two-phase commit
Two-tiered client/server approach
QUESTIONS
1. What is a client/server database system?
2. Explain the database server approach to client/server
database.
3. What are the advantages of the database server
approach to client/server database compared to the
file server approach?
4. What is data transparency in client/server database?
Why is it important?
5. Compare the two-tier arrangement of client/server
database to the three-tier arrangement.
6. What is a distributed database? What is a distributed
database management system?
7. Why would a company be interested in moving from
the centralized to the distributed database approach?
8. What are the advantages of locating a portion of a
database in the city in which it is most frequently
used?
9. What are the advantages and disadvantages of data
replication in a distributed database?
10. Describe the concept of asynchronous updating of
replicated data. For what kinds of applications would
it work or not work?
11. Describe the two-phase commit approach to updat-
ing replicated data.
12. Describe
the
factors
used
in
deciding
how
to
accomplish a particular distributed join.
13. Describe horizontal and vertical partitioning in a
distributed database.
14. What
are
the
advantages
and
disadvantages
of
horizontal partitioning in a distributed database?
15. What
are
the
advantages
and
disadvantages
of
vertical partitioning in a distributed database?
16. What is the purpose of a directory in a distributed
database? Where should the directory be located?
17. Discuss the problem of directory management for
distributed database. Do you think that, as an issue,
it is more critical, less critical, or about the same as
the distribution of the data itself? Explain.
EXERCISES
1. Australian Boomerang, Ltd. wants to design a
distributed relational database. The company is
headquartered in Perth and has major operations
in Sydney, Melbourne, and Darwin. The database
involved consists of five tables, labeled A, B, C, D,
and E, with the following characteristics:
Design a distributed relational database for
Australian Boomerang. Justify your placement,
replication, and partitioning of the tables.
2. Canadian Maple Trees, Inc. has a distributed
relational database with tables in computers in
Halifax, Montreal, Ottawa, Toronto, and Vancouver.
The database consists of twelve tables, some of
which are replicated in multiple cities. Among
them are tables A, B, and C, with the following
characteristics.
Table A consists of 800,000 records and is located
in Halifax, Montreal, and Vancouver.
Table B consists of 100,000 records and is located
in Halifax and Toronto.
Table C consists of 20,000 records and is located
in Ottawa and Vancouver.
Telecommunications
Table A consists of 500,000 records and is heavily
used in Perth and Sydney.
Table
B
consists
of
100,000
records
and
is
frequently required in all four cities.
Table C consists of 800 records and is frequently
required in all four cities.
Table D consists of 75,000 records. Records
1-30,000 are most frequently used in Sydney.
Records 30,001-75,000 are most frequently
used in Melbourne.
Table E consists of 20,000 records and is used
almost exclusively in Perth.
costs
among
Montreal,
Ottawa,
and
Toronto
are
relatively
low,
while
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