The ALTER TABLE tablename SET UNUSED COLUMN colname CASCADE CONSTRAINTS statement is apparently used for marking a column as UNUSED..
I tried loking up a few books including Chip Dawes ..However none of the book mention how to Unmark a UNUSED Column.(so that the column becomes visible again while viewing the table definition !!)

Would appreciate if someone could give me the syntax for setting an UNUSED column as USED again
Thanks- Sunnny