FITSIN does not Recognise my FITS Tape

If you attempt to read a FITS magnetic tape with FITSIN, you might receive an error like this

     % fitsin
     % MT - Tape deck /@/dev/nrmt1h/ > /dev/nrmt3l
     !! Object '/DEV/NRMT3L' not found.
     !  DAT_FIND: Error finding a named component in an HDS structure.
     !  /dev/nrmt3l: MAG__UNKDV, Unable to locate device in DEVDATASET

when you enter the device name. The magnetic-tape system uses an HDS  file called the device dataset (DEVDATASET) to store the position of the tape between invocations of Starlink applications.

When FITSIN is given a name, the magnetic-tape system validates the name to check that it is a known device. There should be a devdataset.sdf file (within /star/etc at Starlink sites) containing a list of at least all the available drives at your site. What FITSIN is complaining about above, is that the device you have given is not included in the DEVDATASET file. Now this might be because you mistyped the device name, or that the particular device is not accessible on the particular machine, or because your computer manager has not maintained the DEVDATASET when a drive was added. You can look at the contents of the DEVDATASET with this command.

     % hdstrace /star/etc/devdataset

Oh and one other point: make sure the tape is loaded in the drive. Yes this mistake has happened (not mentioning any names) and it is very hard to diagnose remotely.