Increase size of partition on AIX

Check space
========  
# df -gs 
Filesystem    GB blocks     Free* %Used    Iused %Iused Mounted on
/dev/hd4           2.00      0.98    1%      212     1% /tmp
#
Increase space
=========
# chfs -a size=+3G /tmp
#
Verify space
========  
# df -gs 
Filesystem    GB blocks     Free* %Used    Iused %Iused Mounted on
/dev/hd4           5.00      0.31    1%      212     1% /tmp
#

Note: Command decrease space
# chfs -a size=-3G /tmp