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6. COMMAND SPECIFICATION
6. 20 RESERVE UNIT 16h
Bit
7
Byte
0
1
2
3
4
5
Unused (00b)
RESERVE UNIT reserves the drive for exclusive use by the requesting initiator or another specified SCSI device.
The reservation will remain in effect until one of the following conditions is met:
- The initiator that made the reservation sends another RESERVE UNIT command.
- The drive is released by a RELEASE UNIT command from the same initiator.
- A BUS DEVICE RESET message is received from any initiator.
- A hard RESET condition occurs.
The occurrence of the last two conditions is indicated by the drive returning a CHECK CONDITION status with a sense
key of UNIT ATTENTION on the next command following the condition. It is not an error for an initiator to issue
RESERVE UNIT to the drive if the drive is currently reserved by that initiator. If the drive has previously been reserved
by another initiator, then the drive generates a RESERVATION CONFLICT status.
If, after honoring the reservation, any other initiator then attempts to perform any command except INQUIRY, RE-
QUEST SENSE, or RELEASE UNIT, then the command is rejected with a RESERVATION CONFLICT status. A
RELEASE UNIT command issued by another initiator will be ignored by that reserved logical unit.
3rd Pty:
The Third-Party Reservation option allows an initiator to reserve the drive for another SCSI device. This option is
intended for systems that use the COPY command and is implemented by the drive.
If the Third-Party bit is zero, then the Third-Party Reservation option is not requested. If the 3rd Pty bit is one, a
RESERVE UNIT reserves the drive for the SCSI device specified in the Third-Party Device ID field. The drive
preserves the reservation until any one of the four conditions mentioned above occurs. The drive ignores any
attempt made by any other initiator to release the reservation and returns GOOD status.
An initiator that holds a current reservation may modify that reservation e.g., switch third-parties by issuing another
RESERVE UNIT command to the drive.
If the logical unit has previously been reserved by another initiator, the target returns a RESERVATION CONFLICT
status.
6 - 86
SONY SDT-10000/SDT-11000 DDS Tape Drive
6
5
Logical Unit Number
4
3
Operation Code (16h)
3rd Pty
Third Party Device ID
Reserved
Reserved
Reserved
Reserved
RESERVE UNIT
2
1
0
Reserved
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