I'm looking to upgrade our cisco secondary appliance to PI v3.9.
This is not going to work since once break the HA all the config on the secondary Gone, So you can use that box for testing inline upgrade and restore the backup. But you need to Upgrade Primary is the right approach.
My sucess steps as below :
1. take the config backup
1.1 break the cluster HA
2. take appliance backup / application backup from Primary ( also License backup) - out of the box, not local repo.
3. Upgrade Inline to Prime 3.4 to 3.7 ( backup config) - means appliance and applicatiopn backup out of the box.
Now you are here :
4. Fresh install 3.9 ISO and restore backup.(3.7) only on Primary.
Note : each step take some time several hours, this took me 4 days full upgrade to 3.9 PI
3.10 releasing soon or may be already there, not checked.
5. do fresh installation PI 3.9 on Secondary and join the cluster.