ASH Report Activity Over Time

One of the most informative sections of the ASH Report is the Activity Over Time section. In this section, the ASH report time span is divided into 10 time slots. If the time period is too short or the data too sparse, the resulting report has fewer slots. Slots 2 through 9 are defined as an integer number of minutes of all the same size for easy comparison. So, it is best to compare the inner slots to one another.

Using the Activity Over Time section, you can perform skew analysis by looking for spikes in the Event Count column. This would indicate an increase in the number of processes waiting for a particular event. A spike in the Slot Count indicates an increase in active sessions because ASH data is sampled from active sessions only. In the pictured example, note the circled event. The number of active session samples has increased, and the number of sessions associated with the buffer busy waits event has also spiked. This kind of skew in a slot possibly represents the root cause of the problem being investigated.