upgrade from enterprise 10.2 to 10.8

[L77]

My coworker is working on upgrading our server from 10.2 to 10.8 soon. He said that since we don't have a concurrent license he will need to take the data offline from 10.2, then move all the data over to 10.8 so he can use the existing license for the new server. Are there other options or is this how it works?

My specific questions:

I have built several field apps for staff in ArcGIS online and have published the data as feature layers that live online and are able to be synced for offline use. All of the data I have in the field apps are copies and are not using links to data from our database. Are my apps safe in ArcGIS online when he does the upgrade of the server or is there potential for my data to be lost?

He is really anti using Arcgisonline and using credits. But my supervisor is okay with me storing the field data in ArcGIS Online so I want to make sure I don't lose my work. I have started backing up my data to my desktop to be safe. 

I was thinking the data in ArcGIS Online shouldn't be impacted by the server upgrade if they are all feature classes that have been shared as a web layer but I don't know.

[Scott_Tansley · Accepted solution]

You need to check your licensing, but I understand that Esri typically allows an upgrade period in which you can run side-by-side, as long as only one is truly production.  

Your data/apps in AGOL are safe, they are a true copy.  They'll stay in the same state until after the upgrade and until you start syncing again.

Having data in AGOL can have different reactions from different people.  To comment, we'd need to know more about why there are concerns before commenting.  But, you're right in saying it won't be impacted by a server upgrade.

[L77]

Thank you Scott!

Our services aren't configured to be able to be taken offline, so I can't use them in field maps when I try to download an offline area. I've had to work with copies that I published in ArcGIS Online to be able to download offline areas.