NetWorker does not physically erase data from tape. In order for the data to be unavailable for recovery, you would have to relabel the volume and reuse it.
Hope this helps,
This question may have multiple answers:
1. relabel - make it harder for NetWorker to read the data - not impossible to get data by using third party data recovery experts;
2. write data across all of tape - make it impossible (although CSI can still read anything ) for anyone to read the data; I have used an HP tool to do a destructive write test, before to see if tape was faulty;
What is the reason for this question:
Is it to avoid scrapping the tapes via costly security firm with certification? Encryption will help. Option 2 will avoid insider knowledge of key + stolen tape;
Stop accidental discovery of data? Send tape to vendor to test?
Test/ prepare tape for use - similiar to full format of disk? - Not required. Label will suffice.
Delete data from client file index/ media databases? - label it.
Mikey's answer is also true with the nsrstage command, as although the data is 'moved', the original data stays on tape, and can be scanner'd back in. The media database is modified to show only the second copy.