Cascaded FICON Director configuration – Getting Started with the IBM 2109 M12 FICON Director [Book]

8

Getting Star

t

ed with the

IBM 2109

M12 FICON Di

rector

Channels

and contr

ol unit l

inks can

be attache

d to the

Fibre Chann

el switches in

any

combina

tion, de

pendin

g on c

onfiguratio

n req

uirement

s and o

n av

aila

ble s

wit

ch por

ts.

Shar

ing a

control

unit thro

ugh a Fi

bre Chann

el switch means

that co

mmunicatio

n from

a

number of

channe

ls to th

e contr

ol unit c

an take plac

e either

ov

er

one switch-to-CU lin

k (in

the

case whe

re a con

trol u

nit has o

nly one l

ink to the

Fibre

Channel switch), or

ov

er mult

iple lin

k

interfaces (in th

e case wh

ere a co

ntrol unit ha

s mor

e than one

link to

the Fibr

e Channel

sw

i

t

c

h

)

.

Just one Fibre Cha

nnel l

ink is atta

ched t

o a FICON

channel

in a c

ascaded

FICON Directo

r

configura

tion. Howe

ver

, from

the FC switch (F

ICON Direct

or), the

FICON ch

annel ca

n

communica

te with a number of

FICON CUs on different por

ts

of the secon

d FC s

witc

h. Once

at the con

trol u

nit, the s

ame co

ntrol unit a

nd device add

ressing c

apabili

ty exists as for a

point-to

-point con

figurati

on. Howe

ver

, the com

munication an

d addre

ssing ca

pabil

ity is greatly

increa

sed for the ch

annel when

conne

cted to an

FC switch with th

e abil

ity to us

e the do

main

and por

t addre

ss por

tion of

the 24-bi

t N_P

or

t a

ddress

(8 bits for the domai

n and 8

bits for the

por

t

) to acces

s multiple

control

units. Note tha

t the do

main addr

ess por

tion

of the FC 2

4-bit

por

t

address

is different be

cause th

ere are

two FC switches

in the ch

annel-

to-cont

rol unit

path.

Figure 1-

4 Cascad

ed FICON

Director co

nfiguration

The com

munication

path be

tween a ch

annel

and a cont

rol unit

is comp

osed o

f two different

par

t

s, the ph

ys

ical ch

annel path

and the

logical

path.

In a casc

aded FI

CON Directo

r topo

log

y

,

the physical paths

are the

FC link

s, interconnec

ted

by the FC switches, that provide t

he physical transmis

sion path

between a FIC

ON ch

annel

and a con

trol u

nit.

A FICON

(FC-SB-

2) logic

al path

is the r

elations

hip established

between

a FICON

chann

el

image and

a con

trol uni

t image

f

or co

mmunica

tion du

ring

e

xecution of an

I/O operation

and

present

ation of s

tatus.