ORA-01466 and flashback query

Someone brought this up in one OTN forum post.

I did a quick search on google and found this,
http://www.adp-gmbh.ch/ora/err/ora_01466.html

It seems a viable explanation. However I really need some sort reference to verify the 5 minutes time frame. Why 5 minutes? Not 1 minutes for example.

Then I found metalink note,

Error ORA-01466 while executing a flashback query.
Doc ID:
Note:281510.1

It explains everything.
The reason is because smon_scn_time is updated every 5 minutes in 9i, please note, in 10g smon_scn_time is updated every 6 seconds which is much more reasonable and making it very unlikely to hit the error.