LU 6.2 API Application Programmer's Reference Guide (30294-90008)

Chapter 1 23
The SNA Network and LU 6.2 API
Systems Network Architecture (SNA)
APPC
Communication between LU 6.2 applications is called Advanced
Program-to-Program Communication (APPC). APPC and LU 6.2
allow programs or applications running on different processors to
communicate and exchange data.
When data can be processed at both ends of a communication line,
fewer data transfers are necessary to perform certain transactions. If a
user must run applications on multiple processors to complete a
transaction, a single program on the user’s local system can
automatically start up the remote applications. The user then has to
issue only one command to initiate multiple processes on different
computers.
The following examples illustrate the advantages of APPC. In the first
example, a user at a site without APPC performs a transaction
involving applications on the local processor and a remote processor. In
the second example, a user performs the same transaction using APPC.
An Example Transaction Without APPC
A clerk works in a satellite office of a large company. The satellite office
receives payments from residents in its local area. Payment
information is kept on the local processor for up to three months. Any
payment information older than three months is kept at the central
office on a mainframe computer. The local processor does not have
APPC.
A customer comes in who requires payment information for the last six
months. The clerk must do the following:
1. Log on to the local processor.
2. Run the appropriate application.
3. Gather payment information for the last three months.
4. End the application.
5. Log on to the mainframe at the central office.
6. Run the appropriate mainframe application.
7. Gather the remainder of the payment information.
8. End the application.
9. Log off the mainframe.
If this is a process that has to be repeated many times during the day, it
can become very cumbersome. The clerk must know which information
is located on which computer. The clerk must also be able to run two
different applications in order to retrieve the information.