Hi Sasa,
The same error occurred to our system (SLES 11 SP2, Max DB 7.9.08, SAP ERP EHP6) when I checked the backup tab on MaxDB Studio today. The consequence is that I couldn't display backup history from DB studio and "Automatic log backup" feature is also closed automatically which resulted in DB hang this morning because of full log area. I removed the wrong code from <SID>.knl under /sapdb/<SID>/data/wrk and dbm.knl under ../wrk/<SID> like below but not deleted the whole line. After that I reopened the Studio and can display backup tab successfully.
The possible reason from my side maybe that the file system of the backup destination is full. I'll setup an environment recent days to test and will let you know.
Before:
After:
Regards,
Lei