Symptoms
The tasks are not processed, in the list of active tasks (Home > Operations > Tasks > Active tasks) there are no running tasks (or only 1) and lots of waiting.
Previously there was a lack of diskspace of the BA application sever (which was fixed). In logsrv.out.log there are records similar to
[16-06-18 00:18:03.236 AFWriter TH03626 ERR] Coult not write logs to file . write() failed - written 30 of 56 bytes: No space left on device
[16-06-18 00:18:03.238 AFWriter TH03626 FTL] Thread terminated by throwing an instance of 'N5STLRT3Log6Server9ExceptionE'.
Cause
Initially the issue is caused by the lack of free disk space. Due to #PBA-74563 ("Scheduler does not resume work after no disk space left on device") scheduler did not resume operating after disk space clean up.
Resolution
As a workaround, restart scheduler (or whole ba) after disk spaced is cleaned up:
service pba restart scheduler
or
service pba restart