awr auto purge runtime change

symptoms :  when awr auto purge fails over and over,  it need to delete awr data (wrh$~~) or to increase awr runtime window.

1. get the default setting

   sqlplus / as sysdba

   oradebug setmypid

   oradebug unit_test kebm_dmp_slv_attrs kewrmapsa_

   => default  runtime : 900  cputime : 300

2. increase cputime/runtime 

   sqlplus / as sysdba

   oradebug setmypid

   oradebug unit_test kebm_set_slv_attrs kewrmapsa_ retain retain 3600 3600 retain retain 

   => runtime : 3600 (1 hour)   cputime : 3600 (1 hour)

3.  restore default value

   sqlplus / as sysdba

   oradebug setmypid

   oradebug unit_test kebm_set_slv_attrs kewrmapsa_ retain retain 900 300 retain retain