Just wanted to understand, if I take a full backup and then then lets say there are no backups for a period of time and the full backup gets expired. If I take an incremental backup now, will it backup everything or only the changes that were made after the full backup ( * The full backup has now expired from NBU catalog now).
Will NBU backup only the changed files based on the archive bit ?
Incremental schedule may kick in , however it will take Full backup as , Incremental schedule doesn't have any base Full backup to maintain chain.
Based on archive bit /time stamp as per your environment design it would pick files which are best candidate for backups (Mostly it should backup all mentioned in selection)
I have never tried this - but i expect netbackup would complain about missing full backup and make the first incremental a "full". I can't recommend this in production. But why not try it out on a test sysem for fun ?
Yes - Netbackup per default uses the archive bit. It can be changed to "file last modified" time (it's a option in the client gui on Windows systems).
If you run the incremental backup in this case it will run as a full backup. And during the next attempt when this incremental backup runs it will backup only the changes.