12-10-2010, 09:52 PM
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File Organization Techniques
Record Access Methods
Data Structures
Record Access Methods
Data Structures
.
Physical Design
Provide good performance
Fast response time
Minimum disk accesses
Definitions
Seek time
Average time to move the read-write head
Rotational delay
Average time for the sector to move under the read-write head
Transfer
Time to read a sector and transfer the data to memory
More Definitions
Logical Record
The data about an entity (a row in a table)
Physical Record
A sector, page or block on the storage medium
Typically several logical records can be stored in one physical record.
File Organization Techniques
Three techniques
Heap (unordered)
Sorted
Sequential (SAM)
Indexed Sequential (ISAM)
Hashed or Direct
