Abstract: A data recording/reproducing apparatus for recording and reproducing data to and from a plurality of record mediums that are non-linearly accessible is disclosed, that comprises a recording/reproducing portion for recording and reproducing data to the record mediums, and a controlling portion for controlling the recording/reproducing portion, wherein when the controlling portion detects that data recorded on one of the record mediums is not reproduced, the controlling portion detects a blank time period for which a host system has not accessed the data recording/reproducing apparatus, causes the recording/reproducing portion to reproduce the data from reproducible record mediums in the blank time period and error correction data recorded on another record medium, and re-structures data that is not reproduced with data that is reproduced from the reproducible record mediums and the error correction data.