I have been asked this question many times and for me it boils down to one idea.

You can never have too much of a good thing!

Running tests usually takes a lot of time and effort. There is planning, setup, executing the test, capturing data, and then processing that data. Having to rerun a test just to get some data that wasn’t captured before is a lot of work. That is why capturing everything up front can save a lot of time and aggravation.

A word of caution though. Watch the disk space while capturing. Make sure the drive won’t be filled with performance data. That could cause the test to fail and cause you to start all over again. Worse, parts of the system could become corrupted and require a complete reinstall and setup of the test.

So what do I monitor? Everything!

When using typeperf, nmon, JMX, database metric snapshots, or anything else; I try to capture much more than I need, but not so much so that I am capturing every piece of data possible. With typeperf, you can literally collect over 2000 different metrics. When pulling data from metric collection of a database, there can be hundreds of data points. Metrics about table spaces, buffer pools, resources, even down to the individual query.

Later I’ll discuss how I process this huge amount of data.