A device determines a critical rotation speed of an optical data carrier at which a critical deflection of said optical data carrier may occur. Further, in a transition area from a pit array to a guide groove or from a guide groove to a pit array, the information recording medium is provided with an intermediate area composed of a pit array of which height changes from a height between a bottom and a side of a groove to another height between the bottom and a side of the pit array. When a data value is accessed, the data processing apparatus can begin processing of that data value and, hence, the performance of the data processing apparatus is not reduced.