I have a question, install mode before was a procedure for safe install software. I mean you can install software without commit and if something happened wrong a device perform rollback to before software. My question is now you can't perform upgrade without commit?
Most cases the upgrade go as expected we never seen any issue if the guide lines followed.
To rollback you need to downgrade the software, since you have both the image available in the switch you can use old image if the upgrade fails.
this is technically possible - and we do not know the model of the device and IOS code from to you upgrading, (if you need specific answer you need to provide this information)
Of course I know that I can upgrade, but my question is different - Why I need add command commit?
install add file cat9k_iosxe.17.11.01.SPA.bin activate % Incomplete command.
and router upgrade rommon now with new software after 16.12