5 I had a student who told me that, by simply running the oracle executable from the command line with a massive set of command-line arguments, Oracle would essentially barf and produce a stack dump, which contains sensitive security information. At that point, I asked him not to tell me any more. It's like knowing the root password when you really don't need that information.

6 It is common for IO reads to complete in less than 1 ms. When this occurs, you know non-Oracle caching is involved. No physically spinning device can respond within 1 ms. Obviously, the block(s) requested does not reside in Oracle's buffer cache; otherwise, no wait event would have been posted, but you do know the block resides in some other cache. It could be the file system buffer cache, or perhaps that very nice cache you purchased from your IO subsystem vendor.

7 Another stellar network command is traceroute. "Hangs" in SQL*Net can commonly be discovered by running a few of these.