Info.and DataBase System - 10.9 - 10.11

On-line System :
 Processing of individual transaction from their origin.

Functions:
i)Separate functions can be integrated.
ii)Information can be centralized.
iii)Information can be collected from remote sites.
iv)Computing facilities can be shared.

Examples:
Banking,Stock Exchange,Stock Control

Advantages:
i)Paper Reduction
ii)Complex task elimination.

Distributed Data Processing System
 Decentralization of computer system through multiple computers.

Applications:
i)Reservation system / Sales order.
ii)Process control application.
iii)Printing of Invoice bills.

Advantages:
i)Independent System.
ii)Reduces the load on the host / client computer.
iii)Reduction of data process delay.
iv)Less risk of system break-down.

Disadvantages:
i)Data movement is more and so the complexity increases.
ii)Increased cost for the use of many hardware components.

Files
 Basic unit of storage in a computer.

Types :
Master File---- ---->Permanent by nature.
     Example : Customer ledger , Purchase ledger.
Transaction File--->Temporary by nature.
     Example : Customer Order , Purchase Order.

File Organization :
   Organizing data into records,blocks and access structure.

General Types :
Logical Organization - i)Organized by OS on secondary storage medium.
                                    ii)Depends on type of storage.
Physical Organization-i)Organized by application program.
                                     ii)Depends on type of information.


Types :
i)Sequential or Serial.
ii)Direct or Random.
iii)Indexed.