The server is unable to obtain the device number for the specified drive. This could occur if an invalid device name is specified for the drive or if there is hardware errors.
The drive is temporarily made offline and is not used for tape operations. The server polls the drive at one-half minute intervals to check if the condition has cleared. Once the drives is accessible again, the drive is brought online.
Determine the reason the drive is inaccessible, such as hardware errors reported in the system logs or an invalid device name was specified for the drive. Render any needed corrections to the drive. The drive will be brought online automatically when the polling process detects that is has become accessible.