Dear friend,
Normally the Notice period will be one month but in the most of the organizations it will be 2 to 3 months at Senior level ie., Manager & above. This is specifically to avoid vacuum because getting a suitable person in Senior level takes bit time hence this type procedure exists.
As far as availing leave during the Notice period differs from company to company and most of the organizations don't allow but in case of exigencies the employee is allowed to avail but to that extent the notice period is extended ie., Ex: Notice period is for 2 months, employee submitted his resignation on 15th March and his last working day is 14 May but the employee is allowed to avail leave for 6 days accordingly the last working day will be 20th May. However I opine that the resigned employee will not have that much of interest on the work and in some cases such employees may spoil the culture hence better to relieve the resigned employee at the earliest.
Hope you are clear
Thanks and regards
Kamesh