Not come across this particular error before & there doesn't appear to be much online, but from the
Shared Storage Guide:
"...
Scan Host
Each shared drive has a host that is identified as the scan host. A scan host is the host from which the automatic volume recognition process (avrd) scans unassigned drives. (The robotic daemons scan assigned drives.) A scan host must have data-path access to the drive.
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How the scan host is determined
EMM determines scan hosts; a scan host may be different for each shared drive. The first host in the environment to come online with a non-zero scan ability factor is the initial scan host for its drives.
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The scan host can change
A scan host is assigned for a shared drive until some interruption occurs. For example, one of the following occurs:
■ The socket connection, the host, the drive, the drive path, or the network goes down.
■ The drive is logically placed in the Down mode.
EMM then chooses a new scan host. The scan host temporarily changes to hosts that request tape mounts while the mount is in progress. Scan host changes occur so only one host at a time has access to the drive path.
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So, possibly the ability of this determination of available scan hosts has failed due to communication or tape drive issues?
