wsvcResponseTimeStdDeviation

Standard deviation of response time for the web service.

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 Description

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.

Default parameter attributes

Attribute	Default value
Application class	INET_Websvc_Inst
Command type	PSL
Platform	all
Icon style	graph
Unit	number of standard deviations
Border range	inactive
Alarm1 range	inactive
Alarm2 range	inactive
Scheduling(poll time)	inherits poll time of the collector
Active at installation	yes
Parameter type	consumer
Value set by	wsvcMonitor