ora-06512,ora-04088错误

create or replace trigger XX_WIP_QTY_CEIL_round
  before insert or update on WIP_REQUIREMENT_OPERATIONS
  referencing new as new old as old
  for each row
when (NEW.quantity_issued = 0 and NEW.operation_seq_num > 0 and new.required_quantity is not null)
declare
  l_start_qty number;
  l_uom_flag  varchar2(100); --判断是否为数量单位
  uom_code    varchar2(5);
begin
  select count('X'),primary_uom_code
    into l_uom_flag,uom_code
    from mtl_system_items_b
   where inventory_item_id = :new.inventory_item_id
     and organization_id = :new.organization_id
     and primary_uom_code in ('PCS', 'EA','KG');
  if (l_uom_flag = 1 )  then
    if uom_code in ('PCS','EA') then
    begin
      select nvl(start_quantity, 0)
        into l_start_qty
        from wip_discrete_jobs
       where organization_id = :new.organization_id
         and wip_entity_id = :new.wip_entity_id;
    exception
      when others then
        null;
    end;
    :new.required_quantity := ceil(:new.required_quantity);
    if l_start_qty != 0 then      :new.quantity_per_assembly := ceil(:new.required_quantity)/
                                    l_start_qty;
 
    end if;
    elsif ( uom_code='KG') then
     begin
       select nvl(start_quantity, 0)
        into l_start_qty
        from wip_discrete_jobs
       where organization_id = :new.organization_id
         and wip_entity_id = :new.wip_entity_id;
    exception
      when others then
        null;
    end;
    :new.required_quantity := round(:new.required_quantity,3);
    if l_start_qty != 0 then      :new.quantity_per_assembly := round(:new.required_quantity,3) /
                                    l_start_qty;
     end if;
    end if;
    if :new.mrp_net_flag = 1 then
      :new.mps_required_quantity := :new.required_quantity;
   
    end if;
  end if;
end;ORA-06512：在"APPS.XX_WIP_QTY_CEIL_ROUND",LINE 6
ORA-04088：触发器"APPS.XX_WIP_QTY_CEIL_ROUND"执行过程中出错我的触发器要怎么修改呢。