Use the chfs command to increase, decrease or set the size of a mounted volume / file system on AIX platform.
chfs -a size=54132736 /usr
Sets the size of the /usr mount point to the specified size in bytes. The size can also specified in short form. The below command will set the size of /usr to 25 GB.
chfs -a size=25G /usr
Instead of setting the size, one can also increase the size of a mount point. The below command increases the size of /usr by 1GB
chfs -a size=+1G /usr
Just the way a size increase is possible, a size decrease is also possible. The below command decreases the size of /usr by 1GB.
chfs -a size=-1G /usr
To increase the size of a file system or mount point, you must have enough disk space available on the logical volume. The operation succeeds only if the necessary disk space is available.
When decreasing the size of a file system, you must have the necessary amount of free space on the file system. What this means is if you have a 25GB file system and have 20 GB of data loaded on it, a 2GB size decrease operation would succeed to have a revised sizes of 23GB. However if you had 24GB of data on the file system, you could reduce the size by only 1GB and not by 2GB.