Index File Organization

By

Junaid Ali Siddiqui

 In situations where we want to access

a record directly without scanning all of the records, then we use indexed file organization.

 In this technique two separate files or tables

are created to store records.  Master file

 Index file

1) MASTER FILE: It is that table which contains actual data.

2) INDEX FILE: An index file is a table or other data structure that holds addresses of other individual records of a file which contain only two data fields .  Primary key  Storage address

CONTINUE…  Primary key uniquely identifies each record

and storage address show the secondary storage address where each record is stored.  There are two variation of an indexed file organization: 



Sequential indexed Non sequential indexed

Sequential index 1. In such organization records are stored

sequentially by primary key value and a simple index that normally points to (address to ) a group of records. 2. It is faster than sequential organization, because here first we access an index file an find the address of record where it is stored, then we directly access it by visiting that address. 3. The master file contains data which is sequentially stored.

MASTER FILE CLASS # 2 4 6 9

ST NAME Hina Jamil Uzma Khan Asma Urooj Zara Ahmad

SUBJECT OOP DLD

MARKS 45 77

D.B

88

D.S

33

INDEX FILE CLASS # 2 4

Storage Address 1000 1004

6

1008

9

10015

CONTINUE… Now here if we want to search record

having Class # 6 then first we access the index file from there we find the storage address of this records, when found, then directly goes to storage address= 1008, where record about “ Asma Urooj” will be stored.

  ADVANTAGE: 3.The basic advantage of index file it has a fast

speed. DISADVANTAGE: Requires memory space because two files

are created. If an index fails to operate, the whole system fails.

S E E M

E G A

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