Detecting a servo error on a magnetic tape and identifying extent and location of the detected servo error by linked control marks

Apparatus for recording data signals onto a elongated magnetic tape record medium said record medium having a predetermined number of laterally spaced-apart longitudinally-extending data tracks that are accessible by a recording/reading head means said record medium and said head means being relatively movable longitudinally of said record member for accessing any area of Said data tracks on said record member, including, in combination:

• recording means having said head means for recording data in and reading data from said data tracks in a plurality of addressable blocks of said data;
• format means connected to the recording means for indicating that a change in said recording is to occur in a limited longitudinally extending portion of all said data tracks;
• said format means actuating said recording means to abort said recording;
• said format means having tape location means for indicating first and second longitudinal data track locations for defining and indicating a predetermined longitudinal extent of said limited longitudinal portion:
• said recording means having moving means for relatively moving longitudinally said record member and head means to said first longitudinal data track location;
• said recording means responding to said moving means for recording unto said data tracks at said first longitudinal data track location a first tape control mark for identifying by its longitudinally recorded location in said data tracks said limited longitudinal portion and inserting into said first control mark an indication of said second longitudinal track location:.
• said recording means continuing recording data unto said data tracks outside of said limited longitudinal portion;
• said recording means being responsive to recording said first control mark to relatively move said record member head means to said second longitudinal data track location;
• said recording means responding to said move to said second longitudinal data track location for recording unto said data tracks at said second longitudinal data track location a second tape control mark for indicating by the longitudinal position in said data tracks of said second tape control mark an end of said limited longitudinal portion at said second longitudinal data track location and inserting into said second tape control mark an indication of said first longitudinal track location;
• said record member having longitudinal-extending machine-sensible servo indications that indicate a relative position of said record member and said head means laterally of said data tracks, said data tracks and said servo indications being parallel along the length of the magnetic tape;
• said recording means having servo means for sensing said servo indications to servo the head means and record member laterally to a length of said data tracks for laterally centering the head means on predetermined ones of said data tracks to said indicated relative position;
• servo error means in said servo means for detecting and that a predetermined servo error has occurred;
• recovery means in said recording means having first means for responding to said indicated servo error for aborting said recording and generating said indication of said first longitudinal track location;
• said recovery means having continue means for continuing relatively moving longitudinally said head means and said magnetic tape for detecting cessation of said predetermined servo error;
• and
• said recovery means having second means for responding to said continue means detecting and indicating cessation of said predetermined servo error to generate said indication of said second longitudinal data track location;
• whereby said limited longitudinal portion is laterally aligned with said predetermined servo error.