File Organization Techniques. Topics Covered: File Organization Techniques of file organization Serial file organization Sequential file organization Direct file organization Indexed sequential file organization. File Organization:
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Techniques of file organization
Access -> Only way to access records in a serial file, is linear search. i.e. key field value to be located is compared with key field value of each record starting at the first record and read all the succeeding records until the required record is found or until the end of the file is reached.
Deletion -> To delete any record first it is located either sequentially or by skip search and then the record is marked for deletion.
Deletion -> Deletion can be performed randomly from any position by calculating the address.
Prime area: It covers the backing storage device. In prime area records are placed in sequential order i.e. ascending or descending order of key field value. Records are written in prime area when the file is reorganized or created.
Overflow area: It is one in which records are stored when prime area is full.
Indexed area: It is used to store index of the file. Index contains track number and highest key field value on that track.
e.g. if we have a storage device with 5 tracks and 5 records can be stored on each track then indexed organization can be indicated as follows:
Prime areaIndex area
Access -> Records can be accessed in linear form in which all the records are searched starting at the first record and read all the succeeding records until the required record is found or until the end of the file is reached.
In second method given key field value is compared with index to obtain track number for which highest key field value is greater than or equal to given key field value then that particular track is searched sequentially to obtain the record.
Prime areaIndex area
Deletion -> For deletion first the record is searched using indexed sequential method and then marked for deletion.