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Page 4
Strategy
Reset Condition
Unit Attention Condition
Contingent Allegiance Condition
When a reset is issued to the tape drive, the SCSI bus clears all uncompleted
commands, releases all SCSI device reservations, sets the tape drive to default
modes, and returns to the Bus Free phase.
The Unit Attention condition in the tape drive typically results from the following
conditions:
•
A Reset was previously issued to the drive.
•
The drive has just been powered on.
•
A cartridge has been inserted.
•
A log exception condition occurred.
•
The mode pages have been changed.
•
The cartridge has been loaded or unloaded to the Hold position, and the Medium
Auxiliary Memory (MAM) is accessible.
The Unit Attention Condition persists for each Initiator until that Initiator issues a
command other than Inquiry for which the tape drive returns with a Check Condition
Status. If the next command from that Initiator following the Check Condition Status
is Request Sense, then the unit attention sense key is returned.
If the Inquiry Command is received from an Initiator with a pending Unit Attention
Condition before the tape drive reports Check Condition Status, the tape drive
performs the Inquiry Command and does not clear the Unit Attention Condition.
If the Request Sense Command is received from an Initiator with a pending Unit
Attention Condition before the tape drive reports Check Condition Status, the tape
drive reports unit attention sense key and clears the Unit Attention Condition for that
Initiator.
The Contingent Allegiance condition shall exist following the return of Check
Condition and may exist following an unexpected disconnect. The contingent
allegiance condition shall be preserved for the I T x nexus until it is cleared. The
contingent allegiance condition shall be cleared upon the generation of a hard reset
condition or by an Abort message, a Bus Device Reset message, or any subsequent
command for the I T x nexus. While the contingent allegiance condition exists the
drive shall preserve the sense data for the initiator.
While the contingent allegiance condition exists, the drive shall respond to any other
requests for access to the logical unit from another initiator with a Busy status.
Execution of queued commands shall be suspended until the Contingent Allegiance
condition is cleared.
LTO SCSI Interface Manual
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