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Page 108
RESERVE UNIT
Command Descriptor Block
6-Byte Command Descriptor Block
Field Descriptions for 6-Byte Command
10-byte Command Descriptor Block
The Reserve Unit command reserves the drive for exclusive use of the requesting
Initiator.
The drive reservation once established, remains in effect until one of the following
occurs:
•
Another Reserve Unit command arrives from the same Initiator that requested
the current reservation. The new reservation supersedes the current one and
may be the same as the current one. Redundant use of the command is not
considered an error.
•
A Release Unit command arrives from the same Initiator that requested the
current reservation. The drive returns to unreserved mode.
•
A Bus Device Reset Message arrives from any Initiator.
•
A Reset condition occurs.
•
Firmware is updated.
When the drive is reserved, it returns Reservation Conflict Status in response to
most commands received from excluded Initiators. Inquiry, Request Sense, Prevent
Medium Removal (with a prevent bit of zero), and Release Unit commands are
accepted from any initiator.
Bits
Byte
7
6
0
1
Ignored LUN
2
3
4
5
Field
Bytes
Bits
Operation
0
Code
Ignored
1
5-7
Logical
Unit
Reserved
Control
5
Bits
Byte
7
6
0
5
4
3
Operation Code (16h)
Reserved
Reserved
Reserved
Reserved
Control
Description
The Operation code for the 6-byte version of Reserve Unit is 16h.
The LUN field is residual from the SCSI-1 days and is ignored.
All reserved bits must be 0.
See Control Byte Format on page 18.
5
4
3
Operation Code (56h)
LTO SCSI Interface Manual
2
1
0
2
1
0
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