A recording and reproducing apparatus and method which prevents or manages a data loss caused by each of seek operations in recording/reproducing a time-series digital data set, to/from a disk recording media via a buffer. Before recording/reproducing, a check is made, by using a rate of data transfer with the outside, of a data transfer rate in an access to a track where each of the selected sectors lies, and of a seek time for each of changes in tracks, to see if the buffer will overflow/underflow during the period of recording/reproducing. If so, then an input/output data transfer rate is reduced before recording/reproducing to make the check. In case of recording, if there is at least a substitute for a sector which will cause the overflow, the sector is changed to a substitute.