In addition to defining individual CICS® resources, you can use CICSPlex® SM to define and manage the communication links between CICS systems. Rather than identifying each CICS system in a communication network to each of its partners (as RDO requires), you can specify general connectivity information to be used by all the CICS systems in a CICSplex.
For example, to define a communication link between two CICS systems using RDO, you specify:
In other words, for each pair of CICS systems that are to communicate you need four definitions - two connections and two sessions. And each connection and session definition is unique to a given pair of CICS systems. They cannot be reused for different communication links.
With Business Application Services, on the other hand, you create one system link (SYSLINK) for each pair of CICS systems. The system link definition refers to one connection definition and one session definition that describe the nature of the link. And those connection and session definitions can be used by any number of system links that share the same characteristics.
Figure 11 illustrates the resource definitions that are required for CICSPlex SM to interconnect three CICS systems. In this example, the total number of definitions is five, rather than the 12 definitions that would be required by RDO.
To define links between the CICS systems in a CICSplex, you would:
Use the CICSSYS view to identify all of the CICS systems you want to connect. Of course, if you are already using CICSPlex SM, you have already identified your CICS systems. CICSPlex SM uses the CICS system ID (SYSIDNT) you specify to identify the system link.
Use the CONNDEF view to create connection definitions for each type of system link you want to create (such as APPC or EXCI). Similarly, use the SESSDEF view to create an appropriate session definition for each connection. Both connection and session definitions are required for each type of system link in your network.
With the names and system IDs of your CICS systems and the appropriate connection and session definitions in place, CICSPlex SM is ready to generate the connections required to link those systems. To define system links, you can:
Figure 12 provides an overview of the end-user interface views used to define links between CICS systems.