Oracle Message ORA-01451 - column to be modified to NULL cannot be modified to NULL

ERRORcolumn to be modified to NULL cannot be modified to NULL
CAUSEthe column may already allow NULL values, the NOT NULL constraint is part of a primary key or check constraint.
ACTIONif a primary key or check constraint is enforcing the NOT NULL constraint, then drop that constraint.

582427Error due to inconsistent Oracle DDIC