Thanks your advise. I did look into $ORACLE_HOME/admin/DB_NAME/pfile/ before I posted the message in here. As I mentioned earlier, ini.ora is no where to be found except there is a file init.ora.80890943.
I am aware of the spfile locate in $ORACLE_HOME/dbs/spfileDB_NAME.ora and I have the file.
The question is how do I change the parameter for my database if I only have the spfile instead of pfile. and I think I can create the new pfile too right??? How come Oracle returns with INVALID FILE name.