Friday, July 3, 2020

Indexed Sequential File Organization (ISFO)

Indexed Sequential File Access (ISFO)

To improve the query reaction time of a sequential file a kind of indexing technique are often added.  We use the term index file to describe the index and data file to refer to the data records the index is useful small enough to be read into the processor memory. This method is designed based on sequential access. In this an index is created for each file which contains pointers for different blocks.
In this, the index is used to control the pointer while accessing the file.

Advantages of Indexed Sequential file Organization: -

Advantages

1) Quite easy to access.
2) with proper selection with key records in a large file searched and accessed very quickly.
3) Any feed of the record can be used as a key. That key feed can be numerical or alphanumerical.

Disadvantages: -

1) Extra data structure has to be maintained.
These extra data structure maintain in on the disk can use a much disk space.
2) The index file have to be re-organized from time to get rid of improve performance that gradually decreased with addition of the record.



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