Quantum ACL 4/52, Дополнительное руководство

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ACL 4/52 Software Interface Guide
Document 6211225-03
Version 3.0
SCSI Interface 3-5
Abort
The Abort message allows the host to clear the present operation on
the library. Abort can be used as follows with the library:
•
The initiator of an operation can abort that process by sending this
message to the library. This stops the operation of the library at its
next “safe” position. Since only one operation is supported per
library at a time, this message effectively stops all processing.
•
If any other initiators send this message, the library accepts the
message but does not abort any of the operations.
Bus Device Reset
The Bus Device Reset message from a host to the library causes the
library to clear all I/O processes. The Unit Attention condition is set to
indicate that the device has been reset.
Command Complete
The library sends this message to the host after the library has
completed the command operation and sent valid status information
to the host. This message does not indicate that the operation was
completed successfully. Successful completion must be determined by
examining the status information. After sending this message, the
library is ready to accept another command.
Disconnect (from Target to Initiator)
The Identify message from the host indicates if the library can
disconnect during the execution of an operation. When the library
receives a command which cannot be immediately completed and a
disconnect has been allowed, then the library disconnects from the
host while performing the operation. This frees the SCSI bus for other
uses while the operation is in progress.
The library disconnects from the host by sending the host the Save
Data Pointer message (if necessary) just before the Disconnect
message.
Given the nature of the host and library interface it is not expected that
a data pointer will be used by the host. Only data transfers which are
broken into multiple connections will end each successful connection
with a Save Data Pointer and Disconnect message sequence. This
conforms to SCSI-2 standard section 5.6.6.
The SCSI-2 standard also allows an optional host-to-target disconnect
message. The library does not support this option and responds with a
Message Reject if a Disconnect message is received.