Can some one help me in providing a good url or book talking about undocumented initialization parameters?
I know that one can use following to find all undocumented parameters which typically start with '_':

select ksppinm
from x$ksppi
where substr(ksppinm,1,1) = '_';


I also found many urls when tried to search using Google and came across this url where Michael Ault is coming out with a complete book on this:
http://www.robonerd.com/oracle9i_und...d_proposal.pdf