SQL & PL/SQL :: Trigger All DML At All Table Events?

i want to write, just ONE trigger that handles all DMS events at schema level and writes the field changes to a specific log table. i wanna to write like 'FOR EACH FIELD' as for each row (& also each table). it turns in the fields section and if the 'old' and 'new' values isnt same, it triggers this function & writes changes to log.

ex. is like:

FOR EACH ROW
FOR EACH FIELD
if (old.value != new.value)
insert into LOG(..., old.name,new.name) values (..., old.value, new.value)
NEXT // FIELD
NEXT // ROW