<s>
In	O
IBM	B-Device
mainframes	I-Device
,	O
a	O
Cross-system	O
Coupling	B-Device
Facility	I-Device
,	O
or	O
XCF	O
,	O
is	O
a	O
component	O
of	O
z/OS	B-Application
that	O
manages	O
communications	O
between	O
applications	O
in	O
a	O
sysplex	O
.	O
</s>
<s>
Dedicated	O
channel-to-channel	B-Device
links	O
(	O
CTC	O
links	O
)	O
.	O
</s>
<s>
Structures	O
in	O
a	O
Coupling	B-Device
Facility	I-Device
,	O
only	O
available	O
in	O
Parallel	B-Operating_System
Sysplex	I-Operating_System
,	O
not	O
in	O
base	O
sysplex	O
.	O
</s>
<s>
In	O
a	O
parallel	B-Operating_System
sysplex	I-Operating_System
decisions	O
about	O
which	O
of	O
these	O
two	O
transport	O
mechanisms	O
to	O
use	O
for	O
routing	O
a	O
specific	O
message	O
are	O
made	O
dynamically	O
.	O
</s>
<s>
Within	O
a	O
single	O
z/OS	B-Application
system	O
messages	O
are	O
transported	O
using	O
cross-memory	O
services	O
,	O
rather	O
than	O
being	O
routed	O
through	O
either	O
of	O
the	O
physical	O
transport	O
mechanisms	O
.	O
</s>
