If there is no hardware related issue that will actually destroyed data on the tape, just run omnimm -reset_poor_medium <media_id>. It is always good to know what caused the poor state. If it is the age of the tape, increase the pool settings fro condition since virtual media will (hopefully) not getting old. :)
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If the medium has become poor as the result of a backup or device error, the data on it may be recoverable, but you may not want to risk writing to the tape again immediately.
What I have done is to create a pool for such media, and I move them into it for the duration of their protection. When protection has expired, reformat the medium - it might be helpful to assign it a label that indicates it has been reused (I add an * to the label, so LF1234L4 becomes LF1234L4*).
This works for both physical and virtual media.
GTS I&O - "When the job's too big for S.H.I.E.L.D...."