Deciding whether and how to run NIS+ in parallel to NIS--and when to stop--is probably one of the most difficult transition issues you will face. NIS+ provides several features that allow it to operate in parallel with NIS, notably, the NIS-compatibility mode.
If you plan to use NIS-compatibility mode, you have to consider the essential benefit provided by NIS-compatibility mode. You need not make any changes to NIS clients. The essential drawback is that you cannot take advantage of full NIS+ security and hierarchy and you may have to change those clients' domain names.
Figure 4-1 illustrates how you convert from an NIS-only namespace to an NIS-compatible namespace that responds to both NIS and NIS+ requests.