Abstract: A method and system are disclosed to provide a defect map structure that can increase the throughput of a recording apparatus when the recording apparatus accesses a data recording medium. A defect register method according to the present invention includes the steps of detecting initial defective sectors, generating a primary defect map (PDM) where each absolute block address of initial defective sectors (D.ABA) is individually registered, discriminating a series of defective sectors consisting of a plurality of initial defective sectors with continuous D.ABA, which exist in the same track (tracks having the same cylinder identification number CYL and head identification number HED) from the individual resister PDM, and generating a PDM, where this series of defective sectors is registered in a batch, by registering a first absolute block address of the series of defective sectors (D.ABA.ST), and defective sector length (number of defective sectors D.LE) of the series of defective sectors.