table locking

Hi guys,
After a full delete on a table, if a commit is not issued, and if some other user wants to insert new data , his(2nd user's) sqlplus session goes hanging indefinetely. Is there a parameter to set some sort of timeout process and kill the faulty user's session(in this case the 1st user) when he accidentally deletes and say walks out to lunch without committing.
I checked the behaviour for insert operations. If first user inserts a row and does not commit, the 2nd user does not get to see the data that was inserted by first user and not committed. However the 2nd user can continue to work otherwise like inserting fresh rows.
Thanks
manjunath