ADI Prevent/Allow Behavior

David Hawks Hawks at
Tue Jun 15 12:35:54 PDT 2004

* From the T10 Reflector (t10 at, posted by:
* "David Hawks" <Hawks at>

The interaction between the RMC device server and the ADC device server
regarding RMC Prevent/Allow is clearly defined in the ADC specification:

PREVENT ALLOW MEDIUM REMOVAL commands issued to the RMC device server
shall not affect the ADC
device server.

Because of this text, I am sure the ADI WG thought about this issue.
However, we have some concerns.  If the host has prevented medium
removal due to an existing backup operation, what is supposed to happen
when the user requests the autoloader to move the current medium from
the DTD.  According to the spec, the autoloader would issue an unload
command which the ADC device server must honor.  This would cause the
backup to fail.  How is this failure avoided?  I have been told that
existing tape drives do not work this way.  Existing tape drives do not
accept an unload from the autoloader when the host has prevented medium

I am told that the user can request the autoloader move the current
medium from the DTD through means other than the host that is aware of
the backup operation (e.g. another initiator, the autoloader front
panel, a separate connection to the autoloader).

David Hawks
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