Ora-04089 =(

ORA-04089: cannot create triggers on objects owned by SYS


CREATE OR REPLACE TRIGGER ValidateNation
AFTER INSERT OR UPDATE OF Nation ON ALLOWED_NATIONALITY

FOR EACH ROW

DECLARE

rowCount integer;

BEGIN

/* Look for the new nation in the Allowed_nationality Table. */
SELECT Count(*)INTO rowcount
FROM ALLOWED_NATIONALITY PA
WHERE :new.Nation = PA.NATION

/* If the nation doest not exists in the table, then send warning message */
If rowCount < 1 then
DBMS_OUTPUT.PUT_LINE ('An artist with '|| :new.Nation ||' does not exist');

End if;

END;
/


I need a bit of guidance, and I'm a little confused as to what I'm supposed to do.

ORA-04089: cannot create triggers on objects owned by SYS
Seems you have created your application tables in the SYS schema, which is an overprivileged user to be used only for database maintenance.
This is one of the worst things you can do.