CREATE PROCEDURE "informix".sp_ins_protocol (
)
  REFERENCING NEW AS new_protocol FOR "informix".protocol;

  LET new_protocol.n5protocol,
        new_protocol.utc_time,
        new_protocol.n_year =
    reglist:"informix".amk_get_next_id(
        new_protocol.id_dctype,                  
        new_protocol.id_personal
    );

  LET new_protocol.n_protocol =
      (SELECT last_id + 1 -- а тут spr_dctype.last_id не забыли обновить ;)
         FROM spr_dctype 
            WHERE id_dctype = n_val.dctype_p);

END PROCEDURE;

CREATE TRIGGER "informix".on_ins_protocol 
  INSERT ON "informix".protocol 
    REFERENCING NEW AS new_p -- вот это возможно и не нужно в данном конкретном случае
    FOR EACH ROW(
      EXECUTE PROCEDURE "informix".sp_ins_protocol(
      ) WITH TRIGGER REFERENCES
    );

DROP TRIGGER "informix".on_ins_protocol;

CREATE TRIGGER "informix".on_ins_protocol 
  INSERT ON "informix".protocol 
    REFERENCING NEW AS n_val
    FOR EACH ROW(
      EXECUTE FUNCTION reglist:"informix".amk_get_next_id(
        n_val.id_dctype, n_val.id_personal) 
        INTO 
          n_val.n5protocol, 
          n_val.utc_time, 
          n_val.n_year, -- никогда не любил этот вариант с разделителем-запятой между операторами
      INSERT INTO n_val.n_protocol 
        VALUES (
          (SELECT last_id+1 
             INTO n_protocol 
                FROM spr_dctype 
                   WHERE id_dctype = n_val.dctype_p
          )
        );
    );