I created a couple of reports on database activity.
But something strange shows up when creating the same report with a resolution of 1 hour and then creating the same report with a resolution type of 1 day.
The "Active time" shows significantly different results for some users between the two reports.
Every 6 hours PA aggregates the Top active DB users to 6 hours resolution and every 24 it aggregate the data from 6 hours to 1 day resolution, this is done by collecting the top 20 active users (by default it 20, but you can change the number of top dimensions).
The gap in the data can occur because the specific user was one of the top 20 active users in multiple hours, but when we aggregate the data to the 6/24 hours resolution the same user is not one of most 20 active users.
You can change the default number in Performance Analysis Agent Administration.
Go to: History Collection| Collection Settings (tab) |Under SQL Collection you can change the "collect top" to "20".