Magnetic disk apparatus with data track reassigning function

A magnetic disk apparatus comprising:

• a magnetic disk medium having tracks arranged concentrically or spirally,
• a magnetic head for recording or reproducing for said tracks,
• detection means for detecting position information of said magnetic head in the direction of track width during recording,
• decision means for deciding the magnitude of a position error of said magnetic head in the direction of track width using said position information and a plurality of threshold values, and
• means for limiting the recording on a track according to a decision result by said decision means wherein
• when the off-track outbreaks and said magnitude of a position error is decided to be larger than the preset threshold value by said decision means at the time of the recording,
• the writing operation on said track is continued,
• the writing operation on the whole or a part of one track on both sides neighboring to said track is temporarily inhibited by said means for limiting the recording on a track.