About realocate SGA memory

Hi
In our production env, there are two database instances running on one AIX 6.1 server (IBM 550).
Instances names are CFCBO and CFIB. According to the AWR reports and other stats, I have notice followings:

1) SGA use is very low than sga_max allocated
2) Total sga_max_sizes (25G + 12704M) is greater than host memory (32G)
3) Server is running with 30% memory paging.

Please advice me, is there any possibility to reduce sga_max_size of above instances to release memory to OS?


AWR reports details and other stats found

Host mem                                          32G

cfcbo
==============
SGA use                                            16.6G
PGA use                                             1G
%Host Mem used for SGA+PGA        28