Queued Unit Attentions - Quantum DLT 8000 Product Manual

SCSI Description
The tape medium is rewound to Beginning of Partition (BOP, i.e., Beginning of Tape
[BOT]).
Note that the tape drive does not implement the hard reset alternative for bus RESET
processing.
The tape drive recognizes multiple bus resets in succession as well as bus resets of
arbitrarily long duration (powering on conditions). It recovers within the time limits
specified above following the last bus reset.

3.6.3 Queued Unit Attentions

Queued Unit Attentions are implemented on the tape drive and are maintained
separately for each valid LUN for each initiator. Unit Attentions are created as a result
of the following circumstances:
Power on
Bus reset
Bus device reset message
When the media may have changed asynchronously
When another initiator has changed the mode parameters
When a firmware (microcode) update has completed
Two (2) queued Unit Attentions are not unusual. For example, if a drive is powered up
and a cartridge is loaded, "power up" and "not ready to ready transition" Unit Attention
messages are created. Due to a limited number of Unit Attention buffers, if an initiator
does not clear Unit Attentions queued for it, the tape drive at some point stops
generating new Unit Attention messages for the Initiator-Logical Unit (I-L)
combination (existing messages remain queued).
A LOAD command does not generate a Unit Attention message for the initiator that
issued the command, since the transition to ready is synchronous.
3-28 Quantum DLT 8000 Tape System