I haqd this happen to me also. I called it the phantom tapes. Because ADSM is 
changing the acc it can only be private or scratch. 

>>> "Loon, E.J. van - SPLXM" <Eric-van.Loon AT KLM DOT NL> 03/16 10:39 AM >>>
Hi ADSM-ers!
Today I encountered I/O errors on a tape. ADSM reported this like this:

ANR8355E I/O error reading label for volume 0371D8 in drive RMT1
(/dev/rmt1).
ANR8778W Scratch volume 0371D8 changed to Private Status to prevent
re-access.

Changed to Private???? Shouldn't ADSM mark the tape read-only???
How else can I see that there is something wrong with this tape? The only
way to find this out is to compare the Q VOLUME list with the Q LIBVOL list
and manually track the differences.
Is this behavior correct?
Kindest regards,
Eric van Loon