PHYSICAL DATABASE DESIGN - Fundamentals of Database Management Systems - page 238

KEY TERMS

Access Method
B+-tree index
Clustering files
Collision
Cylinder
Data volatility
Data volume
Database performance
Denormalization
Derived data
Disk
Division-remainder method

File organization
Fixed disk drive
Hashing method
Head switching
Horizontal partitioning
Index
Logical view
Overflow records
Performance
Physical database design
Platter
Repeating groups

Response time
Rotational delay
Search attribute
Seek time
Subset tables
Text attribute
Throughput
Track
Transfer time
Vertical partitioning
View

QUESTIONS

c. Can an index be built over a combination of fields
as well as over a single field?
d. Is there a limit to the number of indexes that can
be built for a file?
e. How is an index affected when a change is made
to a file? Does every change to a file affect every
one of its indexes?
f. Can an index be used to achieve sequential
access? Explain.
12. Describe the idea of the hashed file. What are
its advantages and disadvantages in comparison to
indexes?
13. Describe how a direct search works in a hashed file
using the division-remainder method of hashing.
14. What is a collision in a hashed file? Why do
collisions occur? Why are they of concern in the
application environment?
15. What is physical database design?
16. Describe why physical database design is necessary.
17. Explain why the need to perform joins is an
important factor affecting application and database
performance.
18. Why does the degree to which data is dispersed over
a disk affect application and database performance?
19. Explain why the volume of data access operations
can

1. Describe the following disk concepts or compo-
nents.
a. Platter and recording surface.
b. Track.
c. Cylinder.
d. Read/write head.
e. Access-arm mechanism.
2. Why is it important to store files on a cylinder-by-
cylinder basis?
3. Describe the four steps in the transfer of data from
disk to primary memory.
4. What is a file organization? What is an access
method? What do they accomplish?
5. What is an index? Compare the concept of the index
in a book to an index in an information system.
6. Describe the idea of the simple linear index. What
are its shortcomings?
7. What is an indexed-sequential file?
8. Describe the idea of the B + -tree index. What are its
advantages over the simple linear index?
9. Describe how a direct search works using a B + -tree
index.
10. Describe what happens to the index tree when you
insert new records into a file with a B + -tree index.

11. Answer the following general questions about

indexes:
a. Can an index be built over a non-unique field?
b. Can an index be built over a field if the file is not
stored in sequence by that field?

adversely affect application and database

performance.
20. Which ''input'' is the starting point for physical
database design?