The invention provides a magnetic recording medium, and a magnetic recording and reproducing apparatus. \u2018Suplumthirtyseven\u2019 characterized by heavy and consistent production of early-season yellow-fleshed purple-black plums that have aromatic sweet flavor, excellent juiciness, and high sugar content. In response to determining that a current lock is set at a locked node that prevents a grant to a requested lock, a determination is made as to whether there are different first and second descendant nodes from the locked node at a same level of the tree data structure linked to the requested data set member and the locked data set member, respectively. Moreover, the positioning member has a centering part 8 in its center, the outer diameter of which is adapted to the second central opening of the compact disc.