Copy a single record to a replica table before update using trigger (Oracle 12c)
You can use this format for copying your original values over:

CREATE OR REPLACE TRIGGER update_Trigger
BEFORE UPDATE ON customer
FOR EACH ROW
BEGIN
    IF UPDATING THEN
        INSERT INTO  replica VALUES(:OLD.cID, :OLD.cName, ... );
    END IF;
END;
/


You will need to specify each field you want inserted into replica

This will be slow and cause a lot of network/database traffic if you are updating 1,000s of rows at a time.