>I am trying to backup only "/etc" and nothing else in "slash"

Whereas /etc is a subdirectory of / , 'dsmc i /etc'
will not work unless you defined /etc as a virtualmountpoint.
You could code an inclexcl file and code:
  exclude.dir /
  include /etc/.../*
(remember that the file is read from the bottom-up).
Be sure to exploit the exclude.dir and exclude.fs specifications
available in ADSMv3, which seem to be underutilized.
       Richard Sims, BU