Based on the comparison of the conventional definitions of B-tree and B⁺-tree, and their manipulating algorithms, a new definition of B⁺-tree: RFN-B⁺-tree is presented in order to achieve higher space efficiency and higher availability. Its space efficiency compared with conventional B⁺-tree is analyzed firstly. Then the availability of RFN-B⁺-tree index file in terms of its full-link pointer structure together with two modules that support this availability: random access algorithm based on virtual root node, and node restructuring algorithm are discussed.