The mapping of one Discovery Domain (DD) to a Discovery
Domain Set (DDS). This indicates the DD is a member of
the DDS. To create a row, cIsnsDdsId contains the
DDS ID of the DDS, and cIsnsDdId contains the DD ID
of the DD which will be a member of the DDS. If a DDS is
deleted, then each entry associating the DDS with a DD is
removed. The addition/deletion of DD's in a DDS should be
carefully handled so as to not disrupt a DDS created by a
storage entity through the iSNS protocol directly.