Visara FEP-4600 Planning Guide - Manual (Page 21)

37x5 to FEP-4600 Migration and Planning Guide
707117-003 2-3
Comparing the Options
For most environments the advantages of Option 2 outweigh the advantages of Option 1.
 Option 1 is not support over FICON or the current ESCON (BARR) interface.
 Option 2 uses fewer subchannels (one per physical network interface) versus one
subchannel per PU 2.0 that Option 1 requires. This may not mean much if only a
few PU 2.0 nodes are involved, but can be very important if hundreds are
involved. Option 1 limits support for PU 2.0 sessions through a single ESCON
interface to 256 (the ESCON interface supports a maximum of 256 subchannels).
Option 2 supports 255 PU 2.0 sessions through a single subchannel.
 No change to PU 2.0 definitions in VTAM with option 2 if they are already
defined for use with the Token Ring interface of the 3745.
 Multiple channel interfaces provide redundant ways to access the same PU 2.0
definition in VTAM with Option 2. Option 1 ties the definition to a single channel
address. This means that if you want to provide redundant paths for the PU 2.0 to
take to access the host resources, then redundant Local Major Node PU 2.0
definitions have to be created.
 Resetting a subchannel affects only one PU 2.0 with Option 1 but can affect
several with Option 2.
 New Switched PU definitions can be added without having to take the XCA
interface down. This means that you do not have to reconfigure the FEP-4600 to
add more PU definitions, nor do you have to recycle the interface. For Option 1
environments, you would have to add a new configuration to the FEP-4600 and
perform a Restart any time that you add a new interface. (Note that you will still
have to make a configuration change on the FEP-4600 when the network interface
is SDLC.)
 Option 2 also supports integrated DLSw connections. Integrated DLSw
connections do not support Option 1.