A few years ago, I wrote a note about a bug in 9i that made it difficult to decide whether or not you had a problem with the log writer (lgwr). The problem was that the time spent in wait event “log file parallel write” was not captured properly – so you were reduced to guessing whether the time spent in “log file sync” might actually be an indication of a log file write problem.
Time changes everything – including the available tools and levels of skill of the people doing the trouble – and I see that Riyaj Shamsudeen recently published a note about the same problem.
Riyaj approaches the problem from a different direction, using exactly the right tool for the task, to demonstrate the error directly (rather than relying on modelling, inference and a follow-up check with Metalink as I did in 2005).
[Update 30th Nov 2008:] Here’s another interesting article on a closely related topic from Christian Bilien – in this case from a 10g system.