Thanks for the verification. I was getting mixed answers from support.
And I did test the theory as well.
1) Copy existing Dataset and modify options by adding vardir=/pathto/newlocation
2) Run backup to write new cache files to new location outside of default /var
2a) Monitor backup times
3) After initial backup completes, allow time for data to change and re run backup
3a) Monitor backup times
4) Copy cache files to 2nd new location, create soft-link to 2nd new location, and run backup for a 3rd time
4a) Monitor backup times
While second backup was running, I checked the moved cache file and say it being accessed and updated. That backup completed without issues.
Is there any advantage or use case where having each Dataset write and kept seperate its own cache makes sense or is required/advised? Since many of our datasets are specific per policy this would essentially create a cache per backup group.
And one last question: I copy the current cache files found in /var to a new multiple locations. Each location will be the location of the specific cache files for each dataset. Will the next backup still use the file as a reference and not require a full?