Can I change SGA_TARGET parameter in online? (Oracle 10g)

Hello

i do not want restart instance.

I wonder SGA_TARGET change in online.

Firstly,

SQL> show parameter sga

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

lock_sga                             boolean     FALSE

pre_page_sga                         boolean     FALSE

sga_max_size                         big integer 16G

sga_target                           big integer    12G

I setted SGA_MAX_SIZE=16g , SGA_TARGET =12g

My database is online now.

And then,

I changed SGA_TARGET    as lower value than SGA_MAX_SIZE .

SQL> alter system set sga_target=15g;

System altered.

I change SGA_TARGET in online.

I did not get error.

so..

Is this effected?

i can not want restart instance.