Upakarma is performed every year by brahmins. Similar to the summer vacation in mainstream studies, a Vedic student is also entitled to his share of holidays and vacations. The students are supposed to stop learning new mantras on the purnima of the month of pousha (falling mostly in the middle of January ) and restart on the purnima in the month of sravana. In between they can revise the earlier lessons of Vedas and sastras.
The recommencement of new lessons is marked by upakarma on sravanapurnima. Nowadays, this practice of taking a break has been discontinued even in Vedic schools. Any new lesson learned during the off period is likely to generate desire and anger in the student. Hence kamokarsheet japa is performed as a penance.
The performer performs all his nityakarmas like sandhyavandanam, Samidhadhanam/ oupasanam upto brahmayajnam. Then he performs the upakarma maha sankalpa to assert that he is restarting the studies.
At the end of the sanklapa he takes bath and changes the holy thread. The holy thread is normally changed at the commencement of any auspicious occasion or at the end of inauspicious periods or as and and when it is found broken or dirty.
Then the chief rishis of Yajurveda called kandarshis (kanda means chapter) are propitiated by offering them tarpana and a homa is performed to offer them ahutis of ghee.
Then the student sits in front of his guru and restarts learning of the Veda by chanting the initial portions of the four Vedas, sastras, sutras etc.
Then the homa is completed.
On the next day Gayatri mantra is chanted 1008 times to compensate for any inadvertent omission of Gayatri japa during the past one year.