Unfortunately, when you format media, the Header file, which contains information about where on this tape data is located, is over-written, and there are no DP tools readily available to recover data
If it is just one file to be restored, you MAY be able to use TapeAnalyser to recover it. You did not state the OS-type or version of your media agent, but this utility can be found
UNIX
/opt/omni/sbin/utilns
Windows
Program Files -> Omniback -> bin -> utilns
I have attached the Usage synopsis
I would first move this media into an unused Media Pool, so it does not get over-written by mistake. THen, use any means available to move the tape into a drive
You will need to use Drive Properties to get the SCSI path / device address of this drive. The drive index will tell you what the drive number is (NOTE, the Drive index numbering starts at '1', on many libraries, the drive numbering starts at '0')
Once the tape is in the device, and you have the SCSI path / device address of this drive, run the command
TapeAnalyser -device scsi_path -filename [filename]
(On UNIX-based systems, the 'TapeAnalyser' must start the ./ for the current directory level)
So, for example, suppose that you wanted to restore a file /u01/databases/file1, and you were using a device file for this drive /dev/rmt/1m, the command would look like this
./TapeAnalyser -device /dev/rmt/1m -filename /u01/databases/file1
ON Windows, it is trickier, because I don't know if you need to include the Drive letter
TapeAnalyser -device Tape 3:0:1:0 -filename C:\databases\file1
Other than the usage synopsis, no documentation exists for this utility, and I have never needed to use it. If this doesn't work for you, I'm afraid you are out of luck