ListServ 14.5 (yeah, stuck in the past I know. :)

I'm wanting to add a lot of users to a subscriber list.  This seems to
detail how:

  http://www.lsoft.com/manuals/1.8e/owner/owner.html#_Toc128537006

However, I have a question about the DD= parameter -- what exactly is
this and what do I need to set it to?  Searching through the rest of
the docs this seems to be some sort of database, but I can't find any
reference to it in the config files.

Is MYDD a sane default?  Probably not... how do I determine what I
should be using here?

Thanks much!

Ray