Indexed (indexed sequential) file organisation, Database Management System

Indexed (Indexed Sequential) File Organisation

It organises the file like a big dictionary, i.e., records are kept in order of the key but an index is stored which also allows a type of direct access. The records are kept sequentially by primary key values and there is an index built over the primary key field.

The retrieval of a data from a sequential file, on average, needs access to half the records in the file, making such inquiries not only useless but very time consuming for big files. To improve the query response time of a sequential file, a type of indexing method can be added.

An index is a set of address pairs, index value. Indexing associates a set of objects to a set of orderable quantities, which are generally smaller in number or their properties. Therefore, an index is a mechanism for faster search. While the indices and the data blocks are stored together physically, they are logically distinct. Let us use the word an index file to defines the indexes and let us refer to data files as data records. An index can be small sufficient to be read into the main memory.

A sequential file that is indexed on its primary key is known as an index sequential file. The index permits for random access to records, as the sequential storage of the records of the file gives easy access to the sequential records. An additional feature of this file system is the over flow area. The overflow area gives additional space for record addition without the need to make.

 

 

Posted Date: 3/7/2013 6:17:04 AM | Location : United States







Related Discussions:- Indexed (indexed sequential) file organisation, Assignment Help, Ask Question on Indexed (indexed sequential) file organisation, Get Answer, Expert's Help, Indexed (indexed sequential) file organisation Discussions

Write discussion on Indexed (indexed sequential) file organisation
Your posts are moderated
Related Questions
Write a program within embedded SQL to associative the total trip expenses of the salesman named ‘John' for the relations. EXEC SQL BEGIN DECLARE SECTION; long total_expenses;

Compute the closure (F+) for the following set of the functional dependencies defined on R(a,b,c,d), where F - {c→ a, ab → d, a → b, d → c}, i.e. what are all of the FDs implied b

What are the Objectives of object design After going through this unit, you could be able to: explain steps of object design; discuss algorithms that reduce costs;

let us consider a table having 2200 records and the fixed size of the table to be considered as 25.then how many numbers of table is requredto perform horizontal fragmentation

Partial Key : It is a group of attributes that can uniquely identify small entities and that are related to same base entity. It is sometime named as Discriminator.  Altern

Define upgrade and downgrade? It gives a mechanism for conversion from shared lock to exclusive lock is called as upgrade. It gives a mechanism for conversion from exclusive

What are audit trails? An audit trail is a log of all alters to the database along with information like which user performed the change and when the alter was performed.

Define the five basic operators of relational algebra? Five basic operators of relational algebra are: 1. Union (∪∪∪∪) - Selects tuples which are in either P or Q or in both

Define Assertions in SQL a. An assertion is a predicate that is expressing a condition we wish the database to always satisfy.  b. Domain constraints, functional dependency

what is meant semantic query optimization? how does it differ from other query optimization techniques?