There are two situations when you may see an "Arc Off-line" marker event:
- There are archive gaps (i.e. the online archives on the server are not continuous and there are some "gap" time ranges with no archive file)
- There are archive files on the server where that particular backfilled point did not write any data (e.g. an archive file has start time 1-Apr and end time 2-Apr and the point did not backfill any events into this range).
Note that these "Arc Off-line" markers are not actually archive events. If the reason for the marker is cause number 2, then you can fix this by reprocessing the associated archive files which do not have data for the point (easily identified using the "Arc Off-line" marker timestamps). Otherwise, you could also change the behavior of the marker using the tuning parameter MarkArchiveGaps. See known issue 26495OSI8 for more details.