Disk control method of format write operation using data distance on a track

A method of controlling an access to data performed in response to a read command, wherein the data is recorded as a data record on a track of a recording medium of an external storage system, on the basis of a control information recorded on said track through a format writing operation, said track storing a plurality of data records, an address marker being associated with each data record, comprising the steps of:

• at a time of recording data, storing in a semiconductor memory a length data indicating a position of the last control information recorded on the track of said recording medium in a format writing operation;
• completing said format writing operation without erasing data of a succeeding area of said track;
• at a time of reading data in response to the read command, detecting an address marker indicating each data record on a track of said recording medium;
• detecting whether the read command for reading data on said track of said recording medium includes an access to data at a position exceeding the position represented by the length data based on information of a position associated with one of said detected address markers indicating a predetermined one of said plurality of data records on said track which corresponds to said position of the last control information;
• executing an access to data when the detected address marker does not indicate that the position of the data to be accessed exceeds the position represented by the length data;
• and
• inhibiting executing the access to data on said track when the detected address marker indicates that the position of the data to be accessed exceeds the position represented by the length data.