They are not tracking open files (you may have mixed that with VSS), but rather changed files and they are file system property. I assume he was referring to NTFS (Windows) in which case journals are indeed helping with speed of incremental backups. Check "Windows Change Journal" chapter in administration guide and also MS KB for more details (even admin guide should be enough). I can confirm incremental/differential backups are faster and we no longer see typical issues with archive bits which we had in past (so data volume decreased too). Also issue with renaming is fixed which used to be an issue before.