Most NSAPI programs you used with iPlanet Web Server 4.1 will work in Sun Java System Web Server 6.1 without being recompiled. Some undocumented data structures have been moved out of nsapi.h and are no longer public. If your plugins use any of these data structures, you should re-write them to use accessor functions. The data structures that are now private are defined in nsapi_pvt.h, which is shipped with the build for informational purposes only.
Custom NSAPI plug-ins are not automatically copied to the new server directory. If you have custom plug-ins, make sure you copy your plug-ins to the upgraded path as shown in the magnus.conf of the new server.
For more information on these data structures and the new accessor functions, see the Sun Java System Web Server 6.1 SP10 NSAPI Programmer’s Guide.