We just went through this, having a high percentage of VTL volumes marked FULL 
when they only contained a few MB, when power maintenance in the data center 
went wrong.  We were able to define new volumes, fortunately, but 'move data' 
jobs don't run that fast actually. If maxscratch had been set closer to current 
usage rather than '99999' we would have been saved two weeks of grief.  
Maxscratch can be quite a useful tool in certain circumstances. Perhaps in very 
large environments, the benefit for time spent is not as high.

Keith