Addressing OLTP Solutions with CICS: The Transaction Server ... - Ibm

8.7 Summary
CICS Client for AIX or an AIX CICS region. The overhead that is observed in
the client to a large extent depends on the situation.
For an ECI CICS Client for AIX, the overhead of using workload management
depends on the complexity. The more complex the client, the lower the
overhead. Measurements with a very simple ECI client have shown an
increase in CPU consumption of approximately 20% and no overhead on the
machine running the CICS system. It is important to recognize that the base
cost, that is, the non-Workload-Manager case, was small because of the
simple nature of the ECI program. With a more realistic ECI client program,
you would see a lower overhead.
We observed an increase of approximately 12% in CPU consumption in a
dynamic transaction routing measurement when the CICS for AIX region was
used solely for routing work to one of three back-end CICS for AIX regions.
Again there was no overhead in the routed-to systems.
The overhead of workload-managed DPL requests has not been measured.
This overhead is similar in nature to the dynamic transaction routing case.
For session balancing support, there is only one call to workload
management: when the client initiates a session with a CICS for AIX region.
You may see a slightly extended initial access time, but after that there
should be no impact.
The only CICS SM components running in the server system are the
resource controller and the agent transaction. During periods of activation
or definition, the resource controllers consume CPU. Once this activity has
completed, negligible activity takes place in the resource controller. The
agent transaction within a CICS region wakes up every 5 seconds and looks
at the health of the CICS system. Both components have no measurable
effect on server performance when there is no CICS region activation or
definition work.
CICS SM provides a very effective tool with which to manage your CICS for AIX
configuration. The major functions that CICS SM provides are SPOC, SSI, and
workload management.
SPOC and SSI simplify the costs of administering your CICS for AIX configuration
and thereby reduce the costs. The staff administering the CICS for AIX
configuration no longer has to be aware of the location of the physical machines.
It is possible to act on groups of CICS for AIX systems or just one single CICS for
AIX system. It is not necessary for each of those machines to be accessed
individually in order to define, start, or stop CICS for AIX regions or Encina SFSs.
With workload management it is possible to distribute the incoming work across
the CICS for AIX regions capable of supporting that type of work. It is possible to
improve the availability of applications to their end users by configuring your
environment in a suitable manner. Managing system outage and applying
maintenance can be simplified, while still providing a service to the users.
These are important considerations, which are often overlooked in planning a
new configuration. Minimizing the number and duration of outages is becoming
increasingly important as commercial pressures increase on enterprises.
Chapter 8. Using CICS System Manager for AIX 131