Efficient rewrite using larger codeword sizes

A method, comprising:

• writing, using M write transducers of a magnetic head, a data set to a sequential access medium, the data set comprising a number of sub data sets of fixed size, each sub data set comprising a plurality of encoded data blocks comprising codewords, each codeword comprising a predetermined number of symbols;
• reading, using M read transducers of the magnetic head, the data set in a read-while-write process to identify faulty encoded data blocks, each of the faulty encoded data blocks comprising at least one faulty codeword;
• selecting a particular logical track from a predetermined subset of logical tracks in a rewrite area of the sequential access medium to rewrite the faulty encoded data blocks, the rewrite area being positioned subsequent to a position of the data set on the sequential access medium, wherein the predetermined subset of logical tracks includes D1+D2+1 logical tracks, and wherein 0<D1+D2<M/4;
• and
• rewriting a correct version of a first of the encoded data blocks identified as faulty in a first encoded data block set to the rewrite area of the sequential access medium, wherein only one encoded data block from a particular sub data set is rewritten in a single encoded data block set in the rewrite area.

A computer program product, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the embodied program instructions being executable by a processor to cause the processor to:

• write, by the processor using M write transducers of a magnetic head, a data set to a sequential access medium, the data set comprising a number of sub data sets of fixed size, each sub data set comprising a plurality of encoded data blocks comprising codewords, each codeword comprising a predetermined number of symbols;
• read, by the processor using M read transducers of the magnetic head, the data set in a read-while-write process to identify faulty encoded data blocks, each of the faulty encoded data blocks comprising at least one faulty codeword;
• select, by the processor, a particular logical track from a predetermined subset of logical tracks in a rewrite area of the sequential access medium to rewrite the faulty encoded data blocks, the rewrite area being positioned subsequent to a position of the data set on the sequential access medium, wherein the predetermined subset of logical tracks includes D1+D2+1 logical tracks, and wherein 0<D1+D2<M/4;
• and
• rewrite, by the processor, a correct version of a first of the encoded data blocks identified as faulty in a first encoded data block set to the rewrite area of the sequential access medium, wherein only one encoded data block from a particular sub data set is rewritten in a single encoded data block set in the rewrite area.