Visara FEP-4600 Planning Guide - Manual (Page 40)

Chapter 3. Support of PU 2.1 Nodes
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Option 2 Considerations
This option is the preferred method of connecting PU2.1’s to VTAM. For this option,
PUs are defined to VTAM using Switched Major Node definitions. One or more XCA
definitions are used to provide a path between a LAN interface and the ESCON channel.
SDLC defined PUs pass through a gateway between a virtual LAN interface and the
SDLC interface.
PUs currently attached to the 3745 via Token Ring use Switched Major Node definitions.
In this case the PUs should already be defined to VTAM, and no change in these
definitions should be required. The FEP-4600 will require a minimum of one XCA
definition in VTAM for each network adapter, which can support up to 255 concurrent
DSPUs (this makes use of only one subchannel as compared to the one subchannel per
PU described in option 1). Using the Switched Major Node definitions additionally
allows for redundant paths to be used to gain access to the host definition through
multiple FEP-4600 platforms (and through multiple channel interfaces). This is because
the Switched Major Node definition is not tied to a specific channel address.
This will appear to VTAM as though each of the APPN nodes is attached to the CPU
through the ESCON channel, as shown in the diagram below.