HP LTO 4 FC manual Further details, Supporting the ACI protocol, Recommended ACI time-out values

	7	6	5	4	3	2	1	0
5			Reserved			Encryption	Status	WORM

The Encryption Status bits indicate the current encryption/decryption status of the SSC device server:

Value	Meaning
00b	The device server is currently not performing encrypting or decrypting operations.
01b	The device server is currently performing encrypting or decrypting operations.
10b, 11b	Reserved.

Further details

For more information about ACI, see the ACI Specification supplied by HP.

Supporting the ACI protocol

Software vendors implementing support for attached library devices will need to work closely with the library vendor concerned. See HP’s “Ultrium Automation Cookbook” for more details.

Recommended ACI time-out values

ACI commands fall into three broad classes:

•Commands that the drive executes immediately

•Commands that the drive queues but which it can execute concurrently with auto-mode reads and writes (in other words, streaming operation)

•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 the drive does not support ACI command queuing. However, under exception conditions, command queuing may occur, say 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 these circumstances, the drive will not ignore the overlapped commands but will respond to every command package it had received.

An example of when this may occur if the host issued a long SCSI ERASE command to the drive and the automation controller issued an UNLOAD command, then the drive would not respond to the UNLOAD command until the long erase had completed. If the automation controller timed 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.

42 Supporting Ultrium features

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