Performance degraded after upgrading from 10.2.0.5 to 11.2.0.4

Hi ,

the next program needed less than 10 Minutes to be executed on Oracle 10.2.0.5.0

after the database is upgraded to 11.2.0.4, it needs more than 1 hour !!

I tested it again with alter session set optimizer_features_enable = '10.2.0.5' ;

in this case it runs also in 10 Minutes.

what does the problem in this Case !!

DECLARE

   anz_rec NUMBER(9);

   tiefe NUMBER(3) := 0;

   anz_null number(9) := 0 ;

BEGIN

LOOP

   tiefe := tiefe + 1;

   if tiefe > &maxtiefe. then

      dbms_output.put_line(tiefe || ': Abbruch wegen zu hoher Tiefe');

      EXIT;

   end if;

   delete from rezst_hlp&seq_num.;

   insert into rezst_hlp&seq_num.

   (verd, reznr, firma, rezartnr, rezmge, posnr, subposnr, artnr, mge, ekp)