Oracle has never guaranteed it has completely instrumented it code. This leaves open the possibility for unaccounted for time. If you are counting each millisecond and come up short, one of the possible reasons for this is that Oracle simply did not instrument a piece of code you ran. For this, and many other reasons, I don't expect to account for every little bit of time in my analyses. This may seem like a problem, but I don't believe it is.

Oracle performance analysis is about solving real-life production performance issues. In all my years of using Oracle's instrumentation, Oracle has not misled me in my analysis. The OraPub 3-circle analysis has confirmed and strengthened what Oracle's instrumentation has indicated. This is why I don't get uptight about unaccounted time. My job is to fix real performance issues, not to find the missing 50 ms!

Sure, it's a lot of fun to figure out the response time to the minutia level, and it definitely is good for your image and makes great cocktail party conversations, but the value of this missing time is highly questionable. During a firefight, it's easy to get distracted from the main overriding goal, and trying to account for every microsecond can cause the technical problem solver to stray from the main objective.