Chapter 3. Protected Conversations exploiters 43
3.2 CICS protected conversations
Figure 3-4 depicts the basic components involved in an APPC Conversation.
Figure 3-4 Overview APPC conversation
A connection between LUs is called a session. This connection can pass through
intermediate network nodes. However, LU 6.2 programs do not need to account for the
details of the connection. It makes no difference to the client transaction program whether the
server transaction program is in the same room or thousands of miles away. The LU 6.2 API
is responsible for starting and ending sessions between LUs of type 6.2.
A transaction program
A transaction program is a part of an application program that uses APPC communications
functions. Application programs use these functions to communicate with application
programs on other systems that support APPC. Your transaction program can obtain LU 6.2
services through either of the following APIs:
򐂰 APPC: Advanced Program-to-Program Communication allows transaction programs to
exchange information across an IBM SNA network using the syntax and verbs defined by
IBM for using an LU 6.2 session.
Attention: During APPC/IMS setup, we recommend the following:
򐂰 Define your APPC/IMS LUs for use by APPC/MVS, as well as by any APPC application
program.
򐂰 Use the LTERM and the MOD name in the first segment of your message. Use the
LTERM to change the destination for your output to a non-LU 6.2 device. Use the MOD
name to format error messages.
򐂰 Use a network-qualified LU name. You do not need to have unique names for the LUs
on different systems.
Transaction
Program
A
A
P
I
L
U
Y
Transaction
Program
B
A
P
I
L
U
Z
Conversation
Session
Transaction Programs (TP)
LU 6.2 API Services
Logical Un its (LUs)

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