A mechanism of monitoring activity on a computer which may be applied to measuring the performance of the computer. The computer is configured to track a first set of information relating to at least a first occurrence of at least one scenario on the computer. At least some of the first set of information is evaluated to make a determination about the first occurrence of the scenario. Based on that determination, the computer may be configured to track a second set of information relating to at least a second occurrence of the scenario on the computer, in which the second set of information includes at least some types of information not tracked in the first set of information. The second set of information can then be evaluated.