What is the purpose of Indian Constitution (81st Amendment), Act, 2000?

The purpose behind the 81st Amendment Act, 2000 was to insert a new clause (4B) after clause (4A) in Article 16 of the Indian Constitution. The new clause provided that the unfilled vacancies of a year reserved for SC/ST kept for being filled up in a year as per Article 16, shall be considered separately for filling vacancies in the succeeding year and the previous list will not be considered for filling the 50% quota of the respective year.