Shalinisharma
No it is not necessary to repeat in both exams. If you have passed in practical examination then it will be valid till your third chance compartmental examination.
As per rule 42 A of examination bye laws of CBSE, previous practical marks will be carried forward and accounted for if he /she has passed in practical.
But in case if you have failed in both the exams i.e. practical and theory both then you have to reappear in both the exam.
If he/she fails to pass the examination in two consecutive years after the first attempt he/she shall have to appear in all the subject including practical exam.
I hope this will clear your doubt.