You should run an inventory operation when Backup Exec is started for the first time following a new installation or a product upgrade. When Backup Exec is exited and restarted, it saves information pertaining to the location and contents of all the media from the last Backup Exec session (provided the media in the devices hasn't changed). With this information, Backup Exec can immediately begin processing operations when it is restarted.
When media is changed in a robotic library, you can inventory all of the slots in the robotic library or select the slots to be inventoried. You are not required to re-inventory slots when adding media requested by Backup Exec.
For example, if you are performing a restore operation, and the data is contained on media that is not currently in the robotic library, you are prompted to insert the media for the restore operation. In this case, you are not required to re-inventory the slot where the restore source media is placed.
When media that is not requested by Backup Exec is added or removed from the magazine, you should perform an inventory operation on the changed slots. This updates the media databases so Backup Exec doesn't load and unload each media in the magazine searching for the correct media on which to process jobs. You can select specific slots to inventory. If you swap media often you may want Backup Exec to perform an inventory on the robotic library magazine each time Backup Exec services are started.