SNAX/APC Configuration and Management Manual

Introduction
SNAX/APC Configuration and Management Manual—138787
1-3
LU 6.2 and SNAX/APC Concepts
Rather than establish one LU-LU session between each pair of TPs that need to
communicate, LU 6.2 creates an LU-LU session between two systems and then treats
the LU-LU session as a serially reusable resource—the session may be used by any
number of TP pairs, one after the other. This LU-LU session is available to all TPs on
the two systems. When two TPs communicate through this shared LU-LU session, the
communication is called a conversation (see Figure 1-2
).
The pair of TPs in the conversation have exclusive access to the LU-LU session. When
the conversation ends, the TPs can release the LU-LU session, thus making it available
to another pair of TPs.
Although the two TPs are called the local TP and the remote TP, the identity of the local
and remote TPs is simply a matter of perspective. Either TP may be considered to be the
local TP, and the TP with which it communicates the remote. In this manual, the local
TP is usually the TP running on a Tandem system; the remote TP is usually running on
another vendor’s equipment.
It is often the case that an LU is in session with a number of other LUs in different
nodes: this is known as multiple sessions (see Figure 1-3
). To increase bandwidth and
allow a number of concurrent conversations between two specific nodes, the LUs at each
end can be configured for parallel sessions (see Figure 1-3
). SNAX/APC supports
single, multiple, and parallel sessions.
Figure 1-2. Sessions and Conversations
LU LU
A Session
A Conversation
Transaction
Program
Transaction
Program