As mentioned already, NBU never 'looks' for tapes in the library, it is always 'told' what tapes are there.
Altough we run an 'inventory' from NBU, again this is in fact a 'Dear Library, what tapes do you have and where are they' command.
Therefore, when tapes are not 'seen', it's down to the library hiding them from us for what ever reason.
These reasons include:
License issues - some tape libraries, you have to license the slots, so if you have a license for 100 slots, but put in 200 tapes, you will only ever see half of them.
Partition issues - many physical libaries can be partitioned into 'multiple' libraries, and each of these 'partitioned' libraries appear to NBU as a totally seperate library. In reality, you are talking to the library firmware, and this is doing all the clever stuff to make the libraries appear seperate (in fact, you have kind of turned your physical library into a VTL .... - ok, the tapes are still physical as opposed to disk, but the rest is effectivly virtual). So fo all this to work, you usually have to assign the library slots to a particular partition, if this is not done, the slots will not be visible.
Virtual I/O slots - some libraries have virtual I/O slots. This extends the physical CAP/ MAP, which mights have, for this example, 10 slots. With virtual I/O, you can eject more tapes than the physical CAP/ MAP an hold, lets say 20 tapes. From teh backup software side, the eject is completed immediately, 10 tapes will be in the physical CAP/ MAP, and 10 tapes will be in virual I/O. Once the CAP/ MAP is emptied, the libary moves the other 10 tapes from virtual I/O to the physical CAP/ MAP. The physical I/O slots are invisible to the backup software, so any tapes in these slots will not show up. The bigger IBM libraries have this feature, but it may well be available on other makes as well.
Poor barcode labels - If the physical barcodes stuck on the tapes are not of a high enough quality (typically seen with self-printed labels) the barcodes will not be visible.
Robtest is the tool to use for this - within robtest the 's s' (show slots) command should list all the tapes in the library. If they are missing, you have a library issue, not a NBU issue.
Hope the above helps.
