The first time you boot the system on DYNIX/ptx V4.6, disk labels are written to your boot/swap disks. If you should then need to reboot on your original V4.4/V4.5 root filesystem from the same disk, the boot will fail because DYNIX/ptx V4.4/V4.5 does not understand disk labels.
To enable DYNIX/ptx V4.4/V4.5 to boot properly, you must remove the disk labels. To do this, add the -e flag to your boot path.
# /etc/bootflags 'bootpath=quad(0)pci(0)scsi(0)disk(3) -e'
When the system reaches multiuser mode, remove the -e flag from the permanent bootflags.
# /etc/bootflags 'bootpath=quad(0)pci(0)scsi(0)disk(3)'