The ActiveMonitorStateChangeLog table stores a record of all of the state changes that occurred for all of the active monitors attached to devices in WhatsUp Gold. When a device goes from up to down, or down at least 2 minutes to down at least 5 minutes, a record of this event is recorded in the ActiveMonitorStateChangeLog table. This table's records are viewed in the State Change Timeline and Active Monitor Availability reports in the WhatsUp Gold web interface.
You can control how long state change records are stored in the database by adjusting the Expire state change data after setting on the Program Options - Report data dialog. For more information, see Changing how long report data is stored and the Program Options - Report Data dialog help.
Note: Decreasing this value can take up to 24 hours to take effect.