About Threshold Rules
A threshold rule is a rule that is set on an individual performance counter to monitor system resource usage during a load test. Counter set definitions contain predefined threshold rules for many key performance counters. For more information, see About Counter Sets.
There are two types of thresholds: warning and critical. An alert message notifies you if the threshold rule is violated. You can view threshold violations when you analyze a load test run. For more information, see Analyzing Load Test Runs.
Threshold Rules and Levels
When you create threshold rules in your load tests, you choose between two types of rules:
- Compare Constant
Compare a performance counter value with a constant value.
- Compare Counters
Compare a performance counter value with another performance counter value.
When you create threshold rules you also set the levels for the rule. The levels are the warning threshold and the critical threshold. When you view a load test run, warning level threshold violations are indicated by a yellow symbol, and critical level threshold violations are indicated by a red symbol.
The Alert if Over Property
When you configure a threshold rule you must set the Alert If Over property correctly to achieve your goal.
Set the Alert If Over property to True to indicate that exceeding a threshold is a problem. For example, if the threshold rule is set on % Processor Time, and you want to be alerted if the value is grreater than 90, use the Compare Constant rule type, set the Critical Threshold Value to 90, and set Alert If Over to True.
Set the Alert If Over property to False to indicate that falling below a threshold is a problem. For example, if the threshold rule is set on Requests/Sec, and you want to be alerted if the value is below 50, use the Compare Constant rule type, set the Critical Threshold Value to 50, and set Alert If Over to False.