On upgrading following notices were given:
Could not find SYSTEM\CurrentControlSet\Control\FileSystem\LongPathsEnabled. Long paths will not be supported.
The 2 DMAs that gave that notice run Windows Server 2012.
Should I address these notices, and how?
You can ignore this.
And I would recommend to upgrade the OS. Windows Server 2012 is no longer supported by Microsoft, and therefore also DataMiner no longer supports this.
The LongPathsEnabled option does not exist on Server 2012, previously we silently ignored this, it's possible we no longer ignore this because we no longer support 2012 Server... Anyhow, this option is only enabled because it could cause issues with e.g. the log collector tool, but in general it should not immediately have impact. I would me more concerned about the 2012 OS and already running without updates or security fixes for more than 6 months, unless this server somehow gets extended support...
Bert
Elaborating on Bert's answer: these errors are actively logged since RN 29910 (DataMiner version 10.1.7). On a more recent Windows OS, you can make the configuration of the LongPathsEnabled option in registry key Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem.