If I overwrite a full tape with a new backup, is the tape marked as empty (other than the data I've just written to it, obviously).
The tape is not marked as "empty", it is overwritten by the new backup. Hence, any informaiton present on that tape prior to the new backup will not be available for restore.
When you write data to a tape than the tape inherits properties of the media set (Overwrite and Append)
So if the media set allows to append than the empty portion of the tape is appendable.
If the media set allows to overwrite after certian period than the entire tape becomes overwritable once
the overwrite protection period ends.
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I suspect you totally missed the OP's question. It is:
1. I have a tape that had data on it and it is overwritten...
2. Is the tape marked as empty.
Bhavik answered it correctly. The question has nothing to do with Append/OPP settings. The previous data is gone. That was the underlying question...
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Correct me If I'm wrong, as per OP tape is being overwritten by a new backup so the tape is
having new backup set along with the properties of the media set. So the tape is not marked
as empty but its either appendable to overwriteable.