Oracle Procedure Aufruf im Trigger

create or replace 
procedure add_flugstunden
  (
  p_per_nr in osq01_pilot.per_nr%TYPE,
  p_bez in osq01_flug.f_bez%TYPE
  )
  is
  BEGIN
   	declare
    	cursor cur_get_data
    	is
    		select
      			pil.p_std,
      			flg.zeit
    		from
      		osq01_pilot pil,
      		osq01_flug flg,
      		osq01_abflug aflg
    		where
      			aflg.f_bez = flg.f_bez and
      			aflg.per_nr = pil.per_nr and
      			aflg.f_bez = p_bez
    	;
    	
    	v_p_std   osq01_pilot.p_std%TYPE;
    	v_zeit    osq01_flug.zeit%TYPE;
    	
  		begin
    		open cur_get_data;
          fetch cur_get_data into v_p_std, v_zeit;
    			update osq01_pilot
    			set p_std = v_p_std + v_zeit
    			where
      			per_nr = p_per_nr;
    		close cur_get_data;
    	end;
  END add_flugstunden;

create or replace trigger tr_add_flugstunden
after insert or update on osq01_abflug
for each row
begin
  add_flugstunden(:new.per_nr, :new.f_bez);
end tr_add_flugstunden;
/

Fehlerbericht:
SQL-Fehler: ORA-04091: table SGD.OSQ01_ABFLUG is mutating, trigger/function may not see it
ORA-06512: at "SGD.ADD_FLUGSTUNDEN", line 11  
ORA-06512: at "SGD.ADD_FLUGSTUNDEN", line 28  
ORA-06512: at "SGD.TR_ADD_FLUGSTUNDEN", line 2  
ORA-04088: error during execution of trigger 'SGD.TR_ADD_FLUGSTUNDEN'  
04091. 00000 -  "table %s.%s is mutating, trigger/function may not see it"  
*Cause:    A trigger (or a user defined plsql function that is referenced in
           this statement) attempted to look at (or modify) a table that was
           in the middle of being modified by the statement which fired it.
*Action:   Rewrite the trigger (or function) so it does not read that table.

INSERT INTO OSQ01_ABFLUG( F_BEZ, AB_DATUM, PER_NR, HERST, TYP, SER_NR, AB_ZEIT)
VALUES ('LH-341','14.11.06','10010001','Boeing','B737','ba23-0012','10,23')