Length of each record in Variable file
Haven't tried this myself so not sure if it will work!
RECORD IS VARYING IN SIZE FROM 1 TO 10000
DEPENDING ON REPORT-SIZE.
01 REPORT-RECORD PIC X(10000).
77 REPORT-SIZE PIC 9(4) COMP-5.
After reading the record you could examine the contents of the field in working storage called REPORT-SIZE and it will hopefully contain the record length!