The only cases that I can see in the current system codes of completion codes in the user-SVC range are 1D0, 1E0, 1FA, 1FB, 1FC, 2E0, 2F3, 2FB, 2FC, 3FB, 3FC, 4FB, 4FC, 5FB, 5FC, 6FB, 6FC,7D0, 7FB, 8FB, 9FB, AFB, CFB, DFB, EFB. I do not know the history of these (I did happen to look up a couple that are in areas I am associatedwith: 2FC was introduced no later than MVS/XA 2.1.0, and 1FC was introduced much earlier than MVS/XA.). There should not be further encroachment in the user-SVC range (xC8-xFF where x is 1-E).
Given that there is a limited number of system completion codes even possible (4096), there are cases where we choose to "hijack" from our own set (if SVC xx won't use code 9xx, then we might assign 9xx to something else). It also wouldn't surprise me at all if, in the future, Fxx is replaced by Fnn with Reason xx, in order to free up most of the Fxx codes for something more useful. There are no current plans to do this. Peter Relson z/OS Core Technology Design
