Why dbms resource management not reducing the CPU on HP UX platform??

We are testing  dbms resource management on 10.2.0.3
Platform HPUX
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Configure a resource plan
=====
DBMS_RESOURCE_MANAGER.CREATE_SIMPLE_PLAN (
        simple_plan => 'EA_TIME'
       ,consumer_group1 => 'NORMAL'
       ,group1_cpu => 90
       ,consumer_group2 => 'DISCO'
       ,group2_cpu => 10
   );

Thus we then have.
====

SQL> l
  1  select
  2  plan, group_or_subplan, type, cpu_p1, cpu_p2, cpu_p3,  status
  3        from dba_rsrc_plan_directives
  4        where plan = 'EA_TIME'
  5*     order by 1,2,3,4,5,6
SQL> /

PLAN       GROUP_OR_SUBPLAN               TYPE               CPU_P1     CPU_P2     CPU_P3 STATUS
---------- ------------------------------ -------------- ---------- ---------- ---------- ----------------
EA_TIME    DISCO                          CONSUMER_GROUP          0         10          0
EA_TIME    NORMAL                         CONSUMER_GROUP          0         90          0
EA_TIME    OTHER_GROUPS                   CONSUMER_GROUP          0          0        100
EA_TIME    SYS_GROUP                      CONSUMER_GROUP        100          0          0