A number of  CMS6 and CMS7 sites have reported  "hung conditions" whereby
LISTSERV keeps processing reader files  and answers console commands, but
appears  to ignore  all  commands sent  via TELL.  Eventually  you get  a
'LISTSERV not receiving;  IUCV error 001' message and LISTSERV  has to be
re-IPL'ed to solve the problem.
 
The problem seems to be due to the SET SERVER command introduced in CMS6.
With the default setting, CMS is  liable to disable IUCV interrupts under
undocumented and at best obscure conditions; the use of SFS would seem to
make it  more likely to  happen. SET SERVER ON  appears to have  the side
effect of  not making CMS  turn off IUCV  interrupts in this  fashion. So
far, the  problem could not  be reproduced with  SET SERVER ON.  The next
release  of LISTSERV  will issue  this command  at startup,  but CMS6/7/8
sites should include it in PROFILE EXEC for the time being.
 
  Eric