computersarefun put in a request for AIX to auto-grow/shrink filesystems.
Ref: https://www.ibm.com/developerworks/rfe/execute?use_case=viewRfe&CR_ID=114789

This seems more like a monitoring thing than an operating system thing.
Also, handling this as a thin LUN is probably better where possible.
Here is an example script.

Potential improvements:
* Notifications on exceptions
* Config file to track different settings per filesystem
* Also check iused / ifree to handle tiny-files
* Run as a daemon vs from cron.
* Explicit lists of filesystems, or include/exclude lists

#!/bin/ksh
###########
# Run this from cron every minute to automatically resize JFS2 filesystems
# Incorrect limits could cause size flapping for small filesystems.
# We skip things we cannot reduce.

MINFREEPCT=10
MAXFREEPCT=70
MINPPFREE=10

LVLIST=`mount | grep jfs2 | grep /dev/ | awk ‘{print $1;}’ | cut -f 3 -d /`
for lv in $LVLIST ; do
df -gv 2>/dev/null | grep $lv | read device size used free pct iused ifree ipct mountpoint || continue
FREEPCT=$(( $used * 100 / $size ))
VG=`lslv $lv 2>/dev/null | grep “VOLUME GROUP:” | awk ‘{print $6;}’`
PPSIZE=`lsvg $VG 2>/dev/null | grep ‘PP SIZE’ | awk ‘{print $6;}’`
[[ $PPSIZE -gt 0 ]] || continue
#
if [[ $FREEPCT -lt $MINFREEPCT ]] ; then
FREEPPS=`lsvg $VG | grep FREE | awk ‘{print $6;}’`
[[ $FREEPPS -gt $MINFREEPPS ]] && chfs -a size=+1 $mountpoint
continue
fi
#
[[ $FREEPCT -gt $MAXFREEPCT ]] && chfs -a size=-$PPSIZE $mountpoint
#
done