File Organization | Database Management System

File Organization | Database Management System

File Organization : File organization shows that how data is arranged together in the secondary storage devices like magnetic disk. The technique used to represent and store the records on a file is called the file organization. Just as arrays, lists, trees and other data structures are used to implement data organization in main memory, a number of Strategies are used to support the organization of data in secondary memory.

Figure shows the different Strategies of organizing data in the secondary memory. We are Concerned with obtaining data representation for files on external storage devices so that required functions (e.g., retrieval, update) may be carried out efficiently. The particular organization most Suitable for any application will depend upon such factors as the kind of external storage available, types of queries allowed, number of keys, mode of retrieval and mode of update.

  • File organization refers to the relationship of the key of the record to the physical location of that record in the computer file.
  • File organization may be either physical file or a logical file. A physical file is a physical unit, such as magnetic tape or a disk.
  • A logical file on the other hand is a complete set of records for a specific application or purpose.
  • A logical file may occupy a part of physical file or may extend over more than one physical file.

Objective of File Organization

The main objectives of file Organization are as follows:

  1. To provide an efficient method to locate records needed for processing.
  2. To facilitate file creation and its updation in future.
  3. A logical method should be observed to organize records in a file.
  4. File structure should be so designed that it would allow quick access to needed data items.
  5. Means of adding or deleting data items or records from files must be present.

Advantages of File Organization

  1. Fast access to single record or collection of related records.
  2. Easy record adding/update/removal, without disrupting.
  3. Storage efficiency.
  4. Redundancy as a warranty against data corruption.

Types of File Organization

There are two basic ways that the file organization techniques differ. First the organization determines the file’s record Sequencing, which is the physical ordering of the records in Storage. Second, the file Organization determines the set of operation necessary to find particular records. Having particular values in Search-key fields typically identifies individual records. This data field may or may not have duplicate values in file; the field can be a group or elementary item. Some file organization techniques provide rapid accessibility on a variety of Search key; other techniques support direct access only on the value of a single Оџne.

The fundamental file organization techniques are as follow:

  1. Sequential File
  2. Indexed Sequential
  3. Direct file / Hash file