This topic describes how AppDynamics thresholds help you to maintain the service level agreements (SLAs) and ensure optimum performance levels for your system.
Thresholds provide a flexible way to associate the right business context with a slow request to isolate the root cause.
You can apply request thresholds at following levels:
- Thresholds for a business application
- Thresholds for individual business transactions
- Thresholds for slow and stalled transactions and background tasks
- Thresholds for diagnostic sessions
Static and Dynamic Thresholds
A static threshold is a static value, which when exceeded, violates the threshold.
A dynamic threshold is based on a changing value. You can specify dynamic thresholds using either Percentages or Standard Deviation measures.
Percentage deviation defines a threshold based on the moving average of the requests over a certain interval. Default time interval is 2 hours. If the average response time for the last two hours is X milliseconds, and if the request takes the percentage deviation over X ms, the transaction violates threshold.
For example, a transaction occurs at 10:00:01 AM. The average of the requests between 8:00:00 and 10:00:00 is 100 ms and the slow threshold is defined as 20 % over threshold. If the transaction takes 120 ms, it will be considered a slow transaction.
Standard deviation defines a threshold based on the moving average over a certain interval. Default time interval is 2 hours. This means if the average response time for the last two hours is X milliseconds, and if the request takes the standard deviation over X ms, it violates threshold.
For example, a transaction begins at 10:00:01 AM and the slow threshold is defined as 3 times the standard deviation (variation from the mean). If the transaction takes more than 3 standard deviations, it will be considered a slow transaction.