Distributed Processing

Distributed processing means that a specific task can be broken up into functions, and the functions are dispersed across two or more interconnected processors. A distributed application is an application for which the component application programs are distributed between two or more interconnected processors. Distributed data is data that is dispersed across two or more interconnected systems.

When your application is located on one system and the data you need is located on one or more other systems, you must decide whether you should write an application to access the distributed data or write a distributed application.

Use an application that accesses distributed data when:
  • Your application runs in a batch environment. For example, if the function of your application only updates a database, this application can run in a batch environment.
  • Your application does not access large amounts of data on another system.
However, accessing data that is distributed on another system is generally much less efficient than writing a distributed application because the data traffic increases. This may result in a decrease in the efficiency of the system.
Use a distributed application when:
  • The data your application needs resides on another system, and your application expects this data to be processed before receiving it.
  • Your application overwhelms the computing resources on one system. Then, you should divide the application into different functions, and let other systems do some of the processing.
  • Your application performs a specific function that other applications can use. This application can reside on a system accessible by many applications.
  • Your application is online.

Writing a distributed application is a more complex task than writing an application that accesses distributed data. When writing distributed applications, one application communicates with another application. These applications must be in sync with each other—that is, the application making a request must know when the application handling the request is ready to receive the request. In most situations, you will be writing both the requesting and the receiving applications. The two applications will use APPC to communicate.