The LISTSERV log is not a regular  disk file maintained by LISTSERV but a
system file where  VM logs all activity on the  LISTSERV virtual console,
including error  messages from  the system, from  other processes  on the
system such as security managers, and so on. It is important to have this
level of logging  because this is the information you  want, in practice,
when there is a problem with LISTSERV.  The disposition of this file is a
matter or  local policy,  controlled by an  "installation exit"  (a short
program LISTSERV calls to create or close that file and that each site is
free to customize). All this to tell you that the only thing LISTSERV can
do under  the present setup is  close this file  and start a new  one. It
can't be searched in the way you would like.
 
  Eric