after insert update trigger

   I have a table named item_master and I have another table named item_master_copy. I need to capture the changes to the item_master table and then copy the change to the item_master_copy table.

I created an after insert & update trigger on item_master table as follows:

create or replace trigger after_insert_update_item
after insert or update on item_master
for each row
declare
v_reflag char(1);
begin
v_reflag:='0';
if (:new.t$item != :old.t$item) then
insert into item_master_copy
(t$item,
t$dsca,
t$wght,
t$buyr,
reflag)