Three or four years ago I read in an Oracle blog somewhere that a DBA had used for an emergency incident resolution an Oracle 10g feature of real time SQL substitution. Basically, he configured Oracle in way that every time that it received a certain query A it executed another query B instead. No application code change, no schema change, just a simple "execute query B instead of A" type of configuration.
Not that I am planning to use that feature (I can think of some undesirable consequences), but out of curiosity does it really exist? If yes, what is that feature called?