When you go to the Media screen, and click on a tape volume, the above window will appear. You should then click the "Display Current Tape Contents" to see what files are on the tape and get a count of files on the tape. If that tape is mostly empty, you can then click the "Unmigrate Volume" button, which will start the process to make sure that all files on the tape are restored back to disk and marked as not-resident on any tape volume.
When the Unmigrate window opens, you must then confirm that you want to unmigrate that tape by again clicking on the button with the tape volume displayed. That will then start the process of finding all files in /cache that are copied (or only resident) on the selected tape volume. Once all files are identified, a work queue is built of those files and the restore of files only on tape is started back to disk storage. This process will take some time to complete. The window will display the progress.
When the unmigrate is complete, you should repeat the above process to insure that all files are marked as not present on the select tape volume.
