In hp-ux 11.23 a filesystem created with mkfs without mentioning "largefiles" can be converted to largfiles online when the data is still there and without unmounting it also.
A. Enter the following commands:
fsadm -F vxfs -o largefiles /var/tmp/image
mount -o remount,largefiles /var/tmp/image
fsadm -F vxfs /var/tmp/image largefiles
I tried it with a 80GB VXFS volume/ Filesystem with 50% of data in it and successfully converted to largefiles without data loss.
