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30 Using Special Features in Libraries
For full details of how these commands are used, see the Automation
Controller Specification, available from HP.
Recommended ACI Time-out Values
ACI commands fall into three broad classes:
3
Commands that the drive executes immediately
3
Commands that the drive queues but which it can execute concurrently
with auto-mode reads and writes (in other words, streaming operation)
3
Commands that the drive queues but which interrupt streaming operation.
The response time to an ACI command will depend on the type of ACI
command and the activity status of the drive at the time the command is
received.
Note that although the drive does not support ACI command queuing,
queuing can occur in exceptional conditions, for example, if the automation
controller had timed-out the tape drive’s response to a command and either
resent the command or sent another command. In such circumstances, the
drive will not ignore the overlapped commands but will respond to every
command package it had received.
An example of this may occur if the host issues a long SCSI
ERASE
command
to the drive and the automation controller issues an Unload command. The
drive will not respond to the Unload command until the long erase had
completed. If the automation controller times out the drive’s response to the
Unload command and re-sends the command or sends another command,
then it needs to be able to handle the response to the original Unload
command as well as to the subsequent commands.
The following tables list the recommended ACI command time-outs for queued
and non-queued commands.
09h Get Error Info 4Ah Send Firmware Segment
0Ah Acknowledge Attention 4Bh Set Time
4Ch Get Time
Mandatory Commands Optional Commands