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.