When you use the onperf utility, you can scroll
back over previous metric values that are displayed in a line graph.
This is useful for analyzing recent trends.
The time interval to which you can scroll back is the lesser of
the following intervals:
The time interval over which the metric has been displayed
The history interval that the graph-tool Configuration dialog
box specifies
The length of time you can scroll back through
cannot exceed the depth of the data-collector buffer.