What criteria should be adopted for choosing type of file organization.

Choosing a file organization is a design decision, hence it must be done having in mind the achievement of good performance with respect to the most likely usage of the file. 

The criteria usually considered important are:
1. fast access to single record or collection of related records

2. Easy record adding/update/removal, without disrupting (1)
3. Storage efficiency
4. Redundancy as a warranty against data corruption.

Needless to say, these requirements are in contrast with each other for all but the most trivial situations, and it’s the designer job to find a good compromise among them, yielding an adequate solution to the problem at hand. For example, easiness of adding/ etc. is not an issue when defining the data organization of CD ROM product, whereas fast access is given the huge amount of data that this media can store. However as it will become apparent shortly, fast access techniques are based on the use additional information about the records, which in turn competes with the high volumes of data to be stored.
Logical data Organization is indeed the subject of whole shelves of books in the “Database” section of your library. Here we’ll briefly address some of the simpler used techniques, mainly because of their relevance to data management from the lower-level (with respect to a database’s) point of view of an OS.

 Five organization models will be considered:
(i) Pile.
(ii) Sequential.
(iii) indexed-sequential. (iv)Indexed
(v) Hashed.


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