A SESSIONS resource defines the logical link between two CICS® systems
that communicate using intersystem communication (ISC) or multiregion operation
(MRO).
Before two systems can communicate using , they must be logically linked
through one or more sessions. The nature of the logical link determines how
they can communicate. CICS does not use the SESSIONS name when the
definition has been installed in the active system. This name is used only
to identify the definition in the CSD file.
You use the CONNECTION attribute of the SESSIONS resource definition to
name the CONNECTION with which these SESSIONS are associated when they are
installed in the active systems.
Special considerations for different session types are:
- MRO links and sessions
- When you install a SESSIONS definition for MRO, you are telling
CICS about a set of parallel sessions between this CICS and another CICS.
The number of sessions is determined by the SENDCOUNT and RECEIVECOUNT attributes.
The SEND sessions are identified by names created from the SENDPFX and SENDCOUNT
attributes. The RECEIVE sessions are identified by names created from the
RECEIVEPFX and RECEIVECOUNT attributes.
- APPC (LUTYPE6.2) links and parallel sessions
- When you install the SESSIONS
definition, the sessions are grouped (for the benefit of VTAM®) into a
modeset, which is identified by the MODENAME. The individual sessions are
named by a counter; the first session created is named -999, the second -998,
and so on. The value of this counter is retained over a warm or emergency
start. The number of sessions created is controlled by the MAXIMUM attribute
on the SESSIONS definition.
- LUTYPE6.1 CICS-CICS ISC links and sessions
- The way in which the sessions
are identified by CICS depends on the way you defined them, using SENDPFX,
SENDCOUNT, RECEIVEPFX, and RECEIVECOUNT like MRO sessions, or using SESSNAME
as for CICS-IMS™ sessions.
Note: Use
APPC for all new CICS-CICS ISC links.
- LUTYPE6.1 CICS-IMS links and sessions
- When you install the SESSIONS definitions
in the active CICS system, CICS identifies each session by the SESSNAME attribute.
- INDIRECT connections
- Because the association between
an INDIRECT link and the intermediate systems used for communicating with
it is made at installation time, install the definition for the intermediate
system before the definition for the INDIRECT link. If you install the INDIRECT
link first, it remains dormant until the intermediate definition is installed,
and until any other already installed connections that make reference to it
are resolved. For example, System A is indirectly connected with system C
through system B. In system A, install the following definitions in this order:
- The intermediate system:
CONNECTION(B) NETNAME(B) ACCESSMETHOD(IRC) ...
- The INDIRECT link
CONNECTION(C) NETNAME(C) ACCESSMETHOD(INDIRECT)
INDSYS(B) ...