What is dynamic routing?

In a CICSplex, resources (for example, transactions or programs) required by one region may be owned by another region (the resource-owning region). For example, you may have a terminal-owning region that requires access to transactions owned by an application-owning region.

Static routing
means that the location of the remote resource is specified at design time. Requests for a particular resource are always routed to the same region. Typically, when static routing is used, the location of the resource is specified in the installed resource definition.
Dynamic routing
means that the location of the remote resource is decided at run time. The decision is taken by a CICS®-supplied user-replaceable routing program. The routing program may, at different times, route requests for a particular resource to different regions. This means, for example, that if you have several cloned application-owning regions, your routing program could balance the workload across the regions dynamically.

All the following can be dynamically routed:

Some further definitions are necessary:

Requesting region
The region in which a transaction or other routable request is issued. Here are some examples of what we mean by "requesting region":
Routing region
The region in which the routing program is invoked for route selection. With two exceptions, the requesting region and the routing region are always the same region. The exceptions are:
  1. Some terminal-related START commands:
    • Because a terminal-related START command is always executed in the terminal-owning region, the requesting region and the routing region may or may not be the same. (This is fully explained in Routing transactions invoked by START commands.)
    • The routing region is always the TOR.
  2. Some method requests for enterprise beans or CORBA stateless objects issued inside CICS:
    • An enterprise bean, program, or object on the local EJB/CORBA server calls a method of an object on a remote EJB/CORBA server. The requesting region is the local region on which the method call is issued. The routing region is the listener region on the remote EJB/CORBA server.
Target region
The region in which the routed transaction or request executes.

Related concepts
Two routing models
Two routing programs
CICS transaction routing
Defining indirect links for transaction routing
Related tasks
Defining remote resources for transaction routing
Application programming for CICS transaction routing
Related reference
Appendix A. Intercommunication rules and restrictions checklist
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