IIRC, once it had a stable hold on the tape the drive would begin reading in an effort to locate the start of the data. On old tapes this might take a number of

IIRC, once it had a stable hold on the tape the drive would begin reading in an effort to locate the start of the data. On old tapes this might take a number of retries with the drive rewinding, reading, rewinding, reading... etc. Sometimes it didn't work at all and you were stuck with a bad tape that needed special attention.