Fujitsu M2488 manual Release Unit command 17h, Release Unit CDB Description

M2488 PRODUCT GUIDE		TAPE UNIT SCSI COMMANDS
4-3.22	RELEASE UNIT command 17h
	The RESERVE UNIT and RELEASE UNIT commands serve to resolve contention in multiple-initi-
	ator systems. The RELEASE UNIT command is used to release previously reserved logical units for
	the requesting initiator, or if it is a third-party release, for another specified SCSI device.
	The SCSI device that releases the reservation of the tape logical unit, also automatically releases the
	reservation of the medium changer logical unit, even though the RELEASE UNIT command was
	directed to the tape logical unit. This is because the SCSI device that gains the reservation of the tape
	logical unit also automatically gains the reservation of the medium changer logical unit.
	The RESERVE UNIT and RELEASE UNIT commands are not supported for the medium changer
	logical unit, however, releasing the reservation of the tape logical unit will serve as a method of
	releasing the medium changer logical unit as well.
4-3.22.1	RELEASE UNIT CDB Description

RELEASE UNIT is a six-byte command. The bytes are shown below and described in Table 4-98. Common fields are described in paragraph 4-3.1 on page 4-4.

						BITS
BYTES	7	6	5		4		3		2	1		0
0	0	0	0		1		0		1	1		1
1
		LUN				3rd Party		3rd Party Dev ID				Reserved
2						Reserved
3						Reserved
4						Reserved
5
				Reserved							Flag		Link

Note: Changeable fields in the CDB are shaded.

Table 4-98. RELEASE UNIT Field Description

BYTE	BIT	VALUE	DESCRIPTION
0	0-7	17h	Operation Code.
1	1-3		The 3rd Party Dev ID is the SCSI device for whom a third-party reserva-
			tion has been made.
1	4	0	If the 3rd Party bit is zero, then the initiator that made the non-third-party
			reservation, releases the reserved device.
		1	If the 3rd Party bit is one, the initiator that made a third-party reservation
			for the device specified in the “3rd Party Dev ID” field releases the reser-
			vation for that same device.

April 1997 CG00000-011503 REV. A 4-101