Hello Gopinath,
The second sentence in this statement should actually be: "If you use NI Switch Executive version 1.0, you should not upgrade to IVI Compliance Package 2.1." This is a bug in the Readme file. The IVI Switch Executive version 2.0 works well with the IVI Compliance Package (ICP) 2.x. Also, drivers developed using ICP 2.1 will work with ICP 2.0.
Best Regards,
Vesna Jadric
Instrument Drivers/IVI
National Instruments