Hey Dhathri,

If you have applied for JEE Mains Examination and didn't given the examination then you will not be counted in the list of qualified candidates in JEE mains that is, you will be declared disqualified. I will suggest you to give your second attempt to JEE Mains next year. Score well and get a NIT.

Good luck ahead !  

Hello.

I have found no ans for this but mostly you will not be considered in the ranking list nothing much happens .

Q . Is it mandatory to give the exam twice or can I give once? If I give the exam both the times, which score will be considered?

Ans: No, this is the candidate's choice. Whether he/she wishes to give one attempt or two is entirely up to them. In case they have attempted both the exams, the better of the two scores will be used for the purpose of ranking in the merit list. 

Hope this may help you.