I find it easiest using file-aid
Go in FILEAID>UTILITIES>COPY specify i-o datasets and press enter.
In options give
Subsequent Selection Interval: then repeat the following
Records to select ===> 1 - select this many records
Records to skip ===> 0 - then skip this many records
Number of records to search ===> ALL you have read this many records
Number of records to select ===>100 or selected this many records
EQ/VSAM processing direction ===> B (F = Forward; B = Backward)
Sortin the vsam file, use inrec to reformat a sequence number in front, sort on the sequence number decending, use outrec to format back to original record and stop after 100. you will need another sort to return to the original sequence if needed.