Tuesday, 12 August 2014

COBOL Different File Organizations.

A comparative study of different file organizations to highlight advantages and disadvantages of using different file ORGANIZATIONs for quick reference. 


SEQUENTIALINDEXEDRELATIVE
Slow when the hit rate is low.Slowest Direct Access ORGANIZATION.Wasteful of storage if the file is only partially populated.
Complicated to change (insert, delete, amend)Especially slow when adding or deleting records.Cannot recover space from deleted records.
Most storage efficient.Not very storage efficient. Must store the Index records, the alternate Index records, the data records and the alternate data records.Only a single, numeric key allowed.
Simple ORGANIZATION.Can use multiple, alphanumeric keys.Keys must map on to the range of the Relative Record numbers.
Recovers space from deleted records.Can have duplicate alternate keys.Fastest Direct Access ORGANIZATION.
-Can be read sequentially on any of its keys.Can be read sequentially.
-Can partially recover space from deleted records.Very little storage overhead.

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