Hello
What was the tape status before goes to poor state? Why the tape has been marked as poor?
To use this command is not the solution just a workaround you must analyze why tapes are being marked as poor.
I guess that tape header is corrupted and for this reason is marked as unknown, you can check it with tapeanalyzer tool.
%DATAPROTECTOR%\bin\utilns\TapeAnalyser -device <logical device> -summary
Where <logical device> is the name of the logical device as declared in Dataprotector
exemple: scsi0:1:0:1C
You have to load the tape in the device before lauching the operation.