Quantities expressed as percentages
The performance analysis reports express most quantified data as percentages. In most cases, absolute values (for example, actual number of observations in which execution was in DB2® services) would not, by themselves, be particularly meaningful. This is because the total number of samples chosen for an observation session is somewhat arbitrary. The percentage of activity attributed to a system object, on the other hand, provides a much better measure of the impact of that system object on performance. Furthermore, when expressed as percentages, quantification is likely to remain roughly equal if the sampling frequency and duration parameters are varied.
- CPU Time Percentage
- The percentage expresses
the ratio of attributed CPU to the total CPU time observed. This is
computed by dividing the number of attributed “CPU EXECUTING” observations
by the total number of “CPU EXECUTING” observations and multiplying
that number by 100.
Note that observations of CPU Waiting and CPU Unavailable are excluded from the calculation. The objective is to report the relative demand placed on CPU resources by system objects.
- I/O Activity Percentage of Time
- The percentage reported for I/O activity expresses the ratio of time attributed I/O operations were active to the total observation session elapsed time. Consider an example in which 10,000 observations were made during a 60 second interval. Suppose during 1,500 of these observations, I/O was found to be active for a file with DDNAME=SYSIN. 15 percent would be reported as the I/O activity percentage of time attributed to SYSIN.
- Parallel Activity
- Application Performance Analyzer will
report information about parallel activity. Examples of parallel activity
are:
I/O activity concurrent CPU execution is observed.
Concurrent I/O activity is observed for multiple devices.
Concurrent CPU execution is observed. This is only possible on a system with multiple CPUs (a multiprocessor).