Specifications

Switch Considerations for FICON
Customer Impact
C-2 UltraNet Storage Router 3000 Version 3.2 Release Notes
Customer Impact
Fibre Channel links may fail to properly initialize if these guidelines are not followed. In addition,
having the bb_credits too low will result in device paths not coming online or Fibre Channel aborts
(MVS interface control checks). FICON emulation will fail if all the frames associated with a
device do not cross the same ISL.
Configuring for FICON Cascaded Director (ISL) Topologies
If the MCDATA Ultranet systems are placed between switches in an ISL configuration, the
FibreChannel file should contain the following statement :
SwitchWwnProxy=yes
When configuring with UCM, you will also have the opportunity to indicate an ISL configuration.
ISL failover is not supported when configured for FICON Emulation. If you are running in FICON
Shuttle mode, ISL failover can be used.
Configuring for FICON Point-to-Point or Switched Point-to-Point Topologies
If the MCDATA Ultranet systems are attached directly or in a single switch environment, the
FibreChannel file must have SwitchWwnProxy set to no. See the FibreChannel file documentation
section for more information. In other words, the FibreChannel file should contain the following
statement :
SwitchWwnProxy=no
When configuring with UCM, you will also have the opportunity to indicate a direct or single
switch configuration. Under FICON Port Options select the "F-Port or N-Port" button. See the
sample UCM window below.
Ensuring Sufficient bb_credits are Configured
The addition of McDATA extension equipment to a FICON configuration will generally require
that a minimum of 60 bb_credits be available to all Fibre Channel ports between and including the
end points. In general, the MVS host and devices will have in excess of 60 bb_credits. Many
switches may have default bb_credits of 16. 16 bb_credits will not be sufficient extending a
FICON channel over distance. Having the bb_credits too low will result in device paths not
coming online and Fibre Channel aborts (MVS interface control checks).