Chapter 5. IBM Tivoli OMEGAMON XE performance optimization 167
5.4.4 Situation threshold and interval
IBM Tivoli supplies a set of default thresholds with each IBM Tivoli OMEGAMON
XE solutions. However, the defaults may not be appropriate for your installation.
Adjust the thresholds for each exception to fit the performance standards at your
installation. For example, situations that are part of a
health check process can
use a longer interval such as 30 minutes, whereas situations that detect a
resource shortage condition probably need a more frequent interval.
Some IBM Tivoli OMEGAMON XE products have specific critical threshold
situations for stall and crash prevention that automatically start by default, but this
may not be true for their warning situations. At many sites the warning yellow
lights are ignored, so it would be a waste of processing to distribute and start
these situations. Other sites pay close attention to warning alerts, in which case
the situations should be autostarted. With IBM Tivoli OMEGAMON XE you can
set different intervals for every threshold. Be aware that picking different intervals
will cause higher overhead. Some products, such as IBM Tivoli OMEGAMON XE
for CICS on z/OS, have preselected critical threshold situations for stall and
crash prevention automatically started as a default. However, they do not
autostart any warning situations.
The predefined situations may have more frequent sampling than required by
your environment. Recognize that not all data is equally important, nor is it
equally expensive to collect. Some higher processing exceptions may not be
crucial to availability in your environment. Ideally, you would like to realize huge
benefits at low cost, but this is not always possible. Avoid high processing
requirements and low benefits. The answers may be different for various
applications running under the same subsystem.
IBM Tivoli OMEGAMON XE attempts to have low overhead defaults. However, no
vendor can know your environment or what is relevant to your business
applications. IBM Tivoli OMEGAMON XE was designed to provide in-depth
analysis, as you will need these capabilities to deal with problems when they
have been identified. However, awareness of situations is not necessarily
minimized by selectively disabling data collection. It is best to disable the items
that you can categorize as low benefit with high overhead.
For migration purposes, IBM Tivoli OMEGAMON XE for x on z/OS uses the
same default thresholds as the associated OMEGAMON II component. However,
you can take advantage of new capabilities to selectively disable Warning
thresholds. Follow the instructions in the configuration and customization guide
for your IBM Tivoli OMEGAMON XE product to run KXEMIGR, a utility that
migrates OMEGAMON II critical and, optionally, warning thresholds to be used
as predefined situations in IBM Tivoli OMEGAMON XE.

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