Distribution of Activity over Run Time

The Distribution of activity over run time graph displays a chronological record of the activity level of the program or subsystem and of its primary file access activities. This report can help you determine the highest users of CPU time, particularly among storage devices.

The graph charts the distribution of activity on a horizontal scale with 100 gradations. Each segment represents one percent of the measurement session. Consequently, any point on the chart corresponds to the execution of a task or file access activity during a particular one-hundredth of the measurement session, expressed as a proportion of all activity during that segment. Each point represents 10 percent of full utilization, rounded to the nearest point. Tasks and files that used less than 5 percent will not show any activity. Activity levels over 50 percent are shown in red.

Because file access activities and task execution activities can overlap one another, the percentages in any column can amount to more than 100, depending on the extent of overlap.

Tip

Analysis tips:
This graph gives you an idea of what tasks and files were busy and when. Vertical blank spaces on the graph may be due to wait time for tape mounts. Look at the Wait Time by Module report to see if there is wait in tape activities (End of Volume, Open, Close, and so on). Also look at the I/O Facility Usage report to see which file the wait is associated with. Additional tape drives may help reduce this time.

If the graph shows two or more files to be busy simultaneously, check the Resource Demand Distribution report to see if those files are causing wait. If they are, check the I/O Facility Usage report to see if these files are on the same pack. If these conditions are true and if the files are accessed sequentially, consider moving one or more of the data sets to a different pack to eliminate this contention.

Related topic

Resource-Demand-Distribution

 

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