Hi,
You don't have to follow method you specified. Palo Alto Upgrade requires base version to upgrade first then to next sub code. In your case since you are moving from 9.1.xx to 0.1.6-h6 I would suggest below upgrade path
1. Take backup of firewall you are upgrading with (backup of Device State would be a good option from Device > Settings)
2. DO NOT upgrade if you are working remotely, make sure to have access to Management interface by present in office or remote hands assistance
3. Download all require software on firewall, this would help during facing any issue
4. Proceed to Upgrade 9.1.14-h4 => 10.0.0 => 10.1.0 => 10.1.6-h6 (You don't need to upgrade with 10.0.xx sub version)
T-SHOOT =
1. Here you might face issue post reboot - like you are not able to login in device using GUI or so, I have seen it sends "session logout error" in some cases, but if you are able to login proceed with next path mentioned above
2. If you face error not able to login or data plane not coming up you might still have access to MGMT interface in CLI. here is a link you can still upgrade firewall using CLI till final code
https://knowledgebase.paloaltonetworks.com/kcsArticleDetail?id=kA10g000000PNns
Hope this will solve your problem
Best,
Bharat Rajwanshi
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