Necessary ritual means whatever ritual a pilgrim must observe and if not, he should offer a sacrificial animal.
The Seven Obligations of Hajj:
1. Performing Ihram from Miqat
2. Standing by `Arafah
3. Spending one night in Muzdalifah
4. Spending one night in Mina
5. Shaving the head or cutting hair short (shaving is recommended)
6. Throwing pebbles
7. Farewell Circumambulation
There is agreement among Juristic Schools on the obligatory and necessary rituals of Hajj.