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Section
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20
40
I
40
01
File Organization
For strictly card- and/or paper-tape-oriented
systems, file organization normally is sequential.
Therefore, the following discussion of indexed se-
quential (as in an encyclopedia) vs random organi-
zation (as in shuffled playing cards) is oriented
mainly toward the design of disk data files.
Indexed Sequential Advantages
•
Both sequential and random transactions can
be handled effectively in most cases.
•
Reports arranged in data file sequence can be
obtained without sorting.
•
Control over both the proces sing and the stored
file can be more positive.
•
Less storage space is required.
•
Frequently the entire file need not be online
simultaneously.
Indexed Sequential Disadvantages
•
More core storage may be required because
of index handling routines.
•
Process time is greater for random input
because of index file seeking and processing.
Random Advantages
•
Less core storage is required normally.
•
Process time is less for random input.
Random Disadvantages
•
To maintain access requirements, frequent
reorgan ization may be neces s ary if the file is dynamic.
•
Extensive key analysis and development of
address conversion routines probably are required
for implementation.
A detailed description of the·se techniques may be
found in section 85.
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