stand wrote:What is the key parameter to measure in a loading test that best indicates performance issues?
That's a very non-specific question, and of course a lot depends on the specific situation you are facing.
If we had to guess, based on our extensive (and growing) experience, the one metric that best predicts (or tracks) application performance is the processing time of a key step that involves a server-side database action.
We see this again and again. A multi-step test sequence run 100's of times in a row shows pretty much constant times for all but a few of the steps, and they show wide -- or very wide -- variation. When we look at those steps in detail they almost always involved 2nd level or 3rd level or a combination of multi-level operations.
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