About NetBackup media manager tape drive selection
When NetBackup Enterprise Media Manager (EMM) determines which storage unit to use, it attempts to select a drive that matches the storage unit selection criteria. The criteria, for example, may be media server, robot number, robot type, or density.
Note the following:
EMM prefers loaded drives over unloaded drives (a loaded drive removes the overhead of loading a media in a drive).
If no loaded drives are available, EMM attempts to select the best usable drive that is suited for the job.
In general, EMM prefers non-shared drives over shared drives, and it attempts to select the drive that was least recently used.