AIX offers tools that allow the administrator to change configration files without editing them directly, thus reducing the possibility of causing a service outage caused by a typo in the configuration file, as described in more detail here.
In this example I have a NFS client with a filesystem mounted from the server cosmos in order to change the mount options so that the filesystem is mounted with the options soft and bg (background) I use the following command instead of directly editing /etc/filesystems.
# chnfsmnt -f /cosmos -d /strom -h cosmos -w bg -S
-f Local mount point
-d Remote direcoty
-h Remote host name
-S Makes the mount a soft mount
The chnfsmnt command will edit the /etc/filesystems file and remount the filesystem with new options.
/etc/filesystems/ before chnfsmnt execution:
/cosmos: dev = "/strom" vfs = nfs nodename = cosmos mount = true options = intr account = false
/cosmos: dev = "/strom" vfs = nfs nodename = cosmos mount = true options = rw,bg,soft,intr account = false