If possible - reboot server to give a clean system going into upgrade - (a personal thing).
Backup OS level and VM level (if applicable)
Check system for manually edited files, and copy of manually.
• SMS check /conf/user.def etc
• GW check trac_client_1.ttm, etc.
• On newly installed version, edit the mentioned files, do not copy in old one.
Check disk space from cli with df -k, and remove large files if disk space is low
• find / -type f -size +100000 -exec ls -lh {} \; 2> /dev/null | awk '{ print $NF ": " $5 }' | sort -nk 2,2
Remove old snapshots
Upgrade DA agent
Install latest upgrade tools
Use blink preferably, contains latest HFA, less reboots.
In CPUSE Right Click blink image to be installed and Verify
Start the upgrade, and monitor Blink log - /var/log/blink/<filename>/main_log.elg