2. USAGE GUIDELINES › 2.2 Data Source Background › 2.2.4 CICS CPU Time

2.2.4 CICS CPU Time

The CICS monitors supported by the CA MICS CICS Analyzer are
event-driven rather than interval-driven.  This means they
collect data by intercepting control from CICS at many
specific events during CICS processing.  They do not sample
CICS activity at fixed or random intervals and assume total
system activity is some multiple of the observed activity.
In effect, the monitors observe all CICS activity.

The supported monitors measure CPU time by calculating what
amounts to the running total of CPU time used since CICS was
started at each event.  The difference between the current
CPU time total and the total from the previous event is the
amount of CPU time used since the last event.  This amount is
added into one of several accumulators (one for each division
of CPU time measured), depending on the type of event the
monitor just recognized.  Most monitors calculate CPU time in
two different ways:  "dispatched" time and "real CPU" time.


DISPATCHED TIME AND CPU TIME CALCULATIONS

Dispatched time is the measure of CPU time that includes the
amount of time CICS was involuntarily interrupted for any
reason, such as page faults or interruption by tasks higher
in the operating system's dispatching priority scheme.

CPU time is an accurate measure of the time during which CICS
was in total control of the computer logic unit, executing
instructions.  It does not include the time CICS was
involuntarily interrupted.


USING TWO MEASURES OF CPU TIME

The main reason for collecting both dispatched time and CPU
time is that the ratio between the two can be useful.  If,
for example, the ratio of dispatched time to CPU time
correlates with paging volume, CICS throughput degradations
would likely be caused by paging activity.  The correlation
analyses can be performed with whatever subset of data is
desired to narrow the search for the paging resource
overload.

If the correlation of that ratio does not appear, or is of
particularly low coefficient during certain periods of time,
CICS response degradation would be caused by interference
with other environmental factors within the operating system,
such as higher priority jobs.