Oracle Message ORA-01463 - cannot modify column datatype with current constraint(s)

ERRORcannot modify column datatype with current constraint(s)
CAUSEAn attempt was made to modify the datatype of column which has referential constraints; or has check constraints which only allows changing the datatype from CHAR to VARCHAR or vise versa.
ACTIONRemove the constraint(s) or do not perform the offending operation.