Biswarup -
See the Certification web page:
http://www.netapp.com/us/services-support/university/certification/index.aspx
It includes links to pages for all of the certifications.
Some have sample tests, most of descriptions of the areas of knowledge the tests cover.
There are also links to suggested Instructor Led and Web Based Training for the exams.
Your best prep is to RTFM (Read the Fabulous Manuals) and practice using the NetApp simulators ...
I hope this response has been helpful to you.
At your service,
Eugene E. Kashpureff, Sr.
Independent NetApp Consultant http://www.linkedin.com/in/eugenekashpureff
Senior NetApp Instructor, FastLane US http://www.fastlaneus.com/
(P.S. I appreciate 'kudos' on any helpful posts.)
