Say you have your financial departments which also an OBS structure.
You cannot modify it as an OBS, but you can move the departments around by defining the parent department.
Say then further that while doing that you created more levels than 10 which should not be possible as an OBS.
You then move the departments again so that you have less than 10 levels.
It appears that the higher levels are still visible as OBS levels.
How do you remove the extra levels which do not have any units associated (if you query the units from the prj_obs_units) and which are above 10?