Standard Deviation of Response Time for the URL (pageResponseTimeStdDeviation)

Standard deviation of average URL response time.

This parameter contains the number of Standard deviations above the average for the current value. This parameter is not populated (has No value) if there are less than 100 historical data points. Spurious one-time spikes are eliminated by suppressing ALARM triggers unless the condition occurs on three consecutive polling cycles.

Detailed

Monitoring the Standard deviation in response times can help you spot abnormal performance degradations. If your server statistics tend to follow normal distribution patterns, most collection cycles should result in a Standard deviation of less than 1, while over 95 percent should fall less than two. Because the parameter warns and alarms only on 3 consecutive cycles with Standard deviations of 2 or 3 above mean, spurious one-time spikes in traffic will be suppressed.

Recommendations

For any given polling cycle, there is a known probability that the response rate will deviate by 2 to 3, but it is unlikely that the deviation will persist over 3 consecutive polling cycles. Although this parameter does not automatically trigger alarms, a good starting setting would probably be 2-3 on Alarm 1 (warn) and 3-10 on Alarm 2 (alarm). If you find that, for your environment, this alarm generates too many events, try changing Alarm 1 Range to 3 to 4 and Alarm 2 Range to 4 to 10.

BMC PATROL properties

TrueSight/ BMC Helix Operations Management properties