Full_Description

   Sort does not create work files until it needs them. If Sort
   needs work files, it creates them, places them in the SYS$SCRATCH
   directory, and assigns them SORTWORKn logicals. Usually, there
   is no advantage to requesting more than one work file. However,
   if the available disks are too small or too full for Sort work
   files, you can increase the number of work files to make each
   work file smaller.

   High-performance Sort/Merge: You can also enhance performance by
   assigning each work file to a different disk.