Cannot delete parameter optimizer_index_cost_adj on Oracle 10.2

Hi all,

I want to delete the parameter optimizer_index_cost_adj in Oracle 10.2 as per SAP recommendations, I did the following to remove it from the spfile:

SQL> alter system reset optimizer_index_cost_adj scope=spfile sid='*';

System altered.

but when I restarted Oracle, the parameter was once again set to 10 ! If I try and reset it in memory I get this error:

SQL> alter system reset optimizer_index_cost_adj scope=memory sid='*';

alter system reset optimizer_index_cost_adj scope=memory sid='*'

*

ERROR at line 1:

ORA-32009: cannot reset the memory value for instance * from instance BPA

any help much appreciated !

Stu