Joined: 06 Jun 2008 Posts: 8214 Location: Dubuque, Iowa, USA
All the sort packages tend to try to do the sort in memory first. If there is more data than will fit in memory, work files will be required. So the answer to your question is that it depends upon how many records you're trying to sort, how big they are, how much memory the sort package can allocate, and so forth.
As Robert says, the answer is "it depends". DFSORT can choose among combinations of memory, memory objects, hiperspace, data space and work data sets to do a sort. Which combination is chosen depends on various factors such as the size of the input file. It's best to always give DFSORT the option of using work data sets if they are needed. By default, DFSORT will dynamically allocate work data sets if they may be needed. You would actually have to take specific actions to prevent DFSORT from using work data sets if it may need them.