Radoslaw,
2)
The restriction isn't in the SAN fabric, or anything to do with FC as I'm not aware of any method in
the FC protocol to actually restrict this on a frame basis. Ficon does work over 2 hops and is
actually supported by IBM in some very specific circumstances/configurations, specifically for
remote distances. If you have a look at IBM's qualification letters for Ficon directors you will see
various combinations such as:
z196 Switch<-->switch<---FCIP---->switch<-->switch-->Device.
But there are some restrictions on what you can do with the inner pair of switches, i.e they are not
permitted to have other devices attached so their purpose is purely as extension devices.. in this
instance the extra hops are referred to by IBM as a "hop of no concern"... but as far as FC is
concerned it is still 4 directors with 3 hops.
As to the reason, IBM have stated that there are possible issues - I suspect timing related due to
undetermined pathing through the SAN- and that the effort to fully support this is considerable.
But,as FC exchange based routing is almost with us (I believe there are some outstanding APARs) then
who knows...
Roy
R.S. wrote:
1. A coupling link ISC-3 is available from z/900 to z196, however IBM
claims it's impossible to connect two machines (*). WHY? Is it technical
or political (marketing) reson?
AFAIK it more restrictive: z10 will not connect to z/900 and z196 will
not connect to z/990.
2. FICON cascaded switching and two hops - that mean connection from
host to CU via more than 2 directors.
Q1. What is the reson of such restriction?
Q2. Has anobody tried to do it? Does it seems to work? What symptoms
(messages, error codes) can be observed?
BTW: What is CCIN 2BD2?
Rega
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