i am working on oracle 9.2.0.1.0

I tried to run this command 

Alter system set session_cached_cursors = 200 scope=spfile;

i am getting the error 
ORA-02096: specified initialization parameter is not modifiable with this option

i tried like this also 
Alter system set session_cached_cursors = 100 ;

Please let me know how to set the parameter with out bouncing the database.

I am very thank ful for your help.