v$backup_datafile

I have a scenario where entry exists in v$backup_datafile, but cannot find any corresponding reference in v$backup_piece or v$backup_set_details.

The strange part is that I was able to join v$backup_datafile and v$backup_piece just an hour ago and was getting result (even have it documented with screenshot & all). Now entry exists in v$backup_datafile but none so ever elsewhere (join columns are set_stamp and set_count).

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