Workload balancing of IIOP requests

To balance client connections across the listener regions, you can use either IP routing or connection optimization by means of Domain Name System (DNS) registration.

To balance OTS transactions across a set of cloned AORs, you use distributed routing. To implement distributed routing, you can use either CICSPlex SM or a customized version of the CICS® distributed routing program, DFHDSRP.

Domain Name System (DNS) connection optimization
Connection optimization is a technique that uses DNS to balance IP connections in a sysplex domain. With DNS, multiple CICS systems are started to listen for IIOP requests on the same port (using Virtual IP addresses), and registered with MVS™ Workload Manager (WLM). Each client IIOP request contains a generic host name and port number. This host name is resolved to an IP address by DNS and WLM services.

Connection Optimization using the WLM is described in the OS/390® V2R8.0 SecureWay Communication Server: IP Configuration, SC31-8513-03.

Distributed routing
Distributed routing is used to balance method calls for enterprise beans and CORBA stateless objects across a set of CICS application owning regions (AORs). The dynamic selection of the target is made by the workload manager—CICSPlex SM or a user-written distributed routing program—which selects the least loaded or most efficient application region. CICS invokes the workload manager for method requests that will run under a new, or no, OTS transaction, but not for method requests that will run under an existing OTS transaction; these are directed automatically to the AOR in which the existing OTS transaction runs. See the CICS Customization Guide for guidance on writing a customized distributed routing program. See the CICSPlex® System Manager Managing Workloads for information about CICSPlex SM Workload Management.

The following diagram shows a CICS logical server. In this example, the listener regions and AORs are in separate groups, connection optimization is used to balance client connections across the listener regions, and distributed routing is used to balance OTS transactions across the AORs.

Figure 1. A CICS logical server. In this example, the logical server consists of a set of cloned “listener” regions and a set of cloned AORs. Connection optimization by means of dynamic DNS registration is used to balance client connections across the listener regions. Distributed routing is used to balance OTS transactions across the AORs.
The picture shows a sysplex containing a logical EJB server. The server consists of multiple cloned listener regions and multiple cloned AORs. Each AOR supports the same set of enterprise beans. Connection optimization by means of dynamic DNS registration is used to balance client connections across the listener regions. Distributed routing is used to balance OTS transactions across the AORs.