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The Response Time Histogram displays response times for selected servers.

To view the histogram, select ANALYZE > Graphs > Statistics > Histogram.

The histogram consists of 10 individual bars.

Each bar represents the percentage of replies within a given milliseconds interval.

This way you can very quickly find out if a particular server is potentially overloaded—like the blue one Image Removed Image Added in the example image.Image Removed

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In the example, we use the histogram to spot a potentially overloaded server. However, the main benefit of the histogram is that it helps you verify if a high average response time is caused by a major or a minor ratio of the total requests. This in turn can help you determine whether a high average response time is really a problem.

How can a high average response time not be a problem?  If a high average response time is caused by a few responses in the 2000-500000 milliseconds interval while the majority of responses are in the 0-10 milliseconds interval, the high average may not be a problem. This of course also depends on your type of organization, which types of applications and servers you run, how business-critical your applications are, etc.

• Servers: Select which servers or server groups you want to base your histogram on. Server groups are enclosed in <>. You can only select server groups and monitored servers. See Server Lists for details about monitored servers.

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  Select multiple servers and server groups by pressing the CTRL key while selecting the servers.

• Agents: Select the group of computers you want to base your histogram on. Super groups, that is groups of groups, are enclosed in <>.
• Interval: Select the period of time that the graph should cover. If the predefined intervals don't suit you, select Custom to specify your own interval.
• Ports: Select which port or port group you want to base your histogram on. Port groups are enclosed in <>. You can only select port groups and monitored ports. See Port Lists for details about monitored ports.