CPU spikes near the end of a large PROC SORT

[Bnad]

This has been an ongoing issue in my company's use of SAS: we run SAS on two powerful unix boxes with dozens of concurrent users.  The boxes are connected to Isilon SAN storage and that is what most users use for read/write/SAS workspace.  (Local and sort workspace are on drives local to the boxes, not on SAN.)  SAS is the only app consuming significant resources on these boxes.

The issue is that we get debilitating CPU usage spikes (freezes the box for 3-5 minutes) on these boxes and from my experience, they always occur when a large PROC SORT is finishing up.  What is PROC SORT doing near the end of its process that consumes so much CPU?  Any suggestions for eliminating these spikes?  (I am not IT; just a user.)

[Astounding]

A few pieces of the puzzle, but definitely not a full answer ...

Toward the end of the SORT process, SAS interleaves the various sort areas, forming the final sorted SAS data set.  There would be a little cleanup after that, such as releasing the sort work areas.

[Bnad]

I should clarify that these spikes/freezes happen really late in the PROC SORT, after the sorted dataset is fully written to disk, but before the PROC SORT finishes.