In a NIS environment there is only one organization unit per enterprise which corresponds to the NIS domain. This orgunit is named orgunit/domainname where domainname is the name of the NIS domain. For example, if the NIS domain name is doc.com, the organizational unit is org/doc.com.
In an NIS environment, you can use an empty string as a shorthand for the organizational unit. Thus, org// is equivalent to org/domainname.