Thanks for answering my question.
We are backing up on an exabyte vxa-2 10-tape changer and we are backing up notes databases (via notes agent) any maybe some sql databases.
The log entry in detail is:
Fehlerkategorie : Andere Fehler
Fehler : 3698 - 0x 3698 (13976)
(Sorry, german language installation).
Meanwhile i did some research myself and i found out the the hd-space available was a bit low.
So i cleaned up the hd.
Also i found some messages that could also be caused by low hd space.
I will see, if the daily backup will run without problems and give you some feedback tomorrow.