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

8.5.2 The Reference System
124 CICS for AIX as the Transaction Server
provide universal access to the data, each CICS system would have to
access the data remotely. This is quite easily done as long as both the CICS
system and Encina SFS are in the same DCE cell. Again though, there is a
performance overhead in accessing an Encina SFS remotely. The most
immediate by-product is that fast local transport cannot be used between the
CICS application server and the Encina SFS.
• Have all of the facilities required
In combining applications in the way in which we have suggested, you must
remember to include all of the facilities that the applications require. For
example, you may have to define more intersystem communication links
because the applications being placed within a region each access different
remote systems.
• Are compatible
Different applications may try to use the same temporary storage or
transient data queue names, for example. If the names cannot be changed,
the conflicting applications would have to remain separate.
• Do not contain any affinities
An application contains an affinity when, for example, it must be run in the
same CICS system because a piece of data or state information that it
requires is in that CICS system. From a workload management point of
view, this is a bad characteristic for an application because it restricts the
flexibility of making routing decisions.
For a fuller description of the problems that you may encounter in running in this
type of environment, see CICS/ESA Dynamic Transaction Routing in a CICSplex,
SC33-1012-00. That book was written with a parallel transaction server
environment in mind but contains useful information that is applicable in a
parallel environment.
8.5.1.5 Summary
You may find that moving to the multiple CICS systems we suggest here requires
significant effort. Indeed it may not be achievable immediately, given the
characteristics of some applications. It is a worthwhile goal to achieve, however,
for a number of reasons:
• Increased application availability
• Better utilization of the available resources
• Good growth capability. As the demands grow on the system, it is possible
•
to produce another instance of the common system and have it added to the
workload management
Transparent maintenance
CICS SM workload management recognizes that machines have different
processing capabilities. If one machine contains a faster processor than
another, all else being equal, the first machine will process more work in a given
period of time.
To deal with these differences in processing capability, workload management
uses a reference system. In an environment in which there are mixed processor
speeds, it is possible to rank machines relative to each other. For example, the
middle speed machine in your configuration might be given a relative speed of 1.
Those machines that are slower would have a value of less than 1, and those
that are faster would have a value of more than 1. If all machines were of