Abstract: If a real memory-backed demand paging virtual store is used as a work device in an external sort, then data movements and processing time are substantially less than that for processing the same external sort in either an internal (real) memory or DASD serving as the work device. Also, reblocking of generated partial sort strings during the sort phase and of the totally ordered string during the merge phase is avoided. The optimum ratio of internal (real) memory backing to the virtual store lies between 30-80 percent. Page faulting is reducible as a consequence of the fact that in the external sorting using the virtual store as a work device, a data element need only be referenced twice.