5.33RESERVE (6) Command (16h)

The RESERVE and the RELEASE commands are used for contention resolution in multiple-initiator systems. The RESERVE command is used to reserve a logical unit. The data format and the field descriptions are described in Table 5-180 and Table 5- 181 respectively.

Table 5-180RESERVE (6) Command Descriptor Block-Data Format

Bit

7

6

5

 

4

 

3

2

 

1

0

Byte

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

Operation

Code (16h)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

Reserved

 

 

3rdPty

 

Third Party Device ID

 

Extent

 

 

 

 

 

 

 

 

 

 

 

2

 

 

 

 

Reservation

Identification

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3 - 4

 

 

 

 

Extent List Length

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5

 

 

 

 

Control

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 5-181RESERVE (6) Command-Field Descriptions

 

 

Field

Description

 

 

3rd Pty

When set to 1, it indicates that the Third Party Device ID field is valid.

 

Required and used only when the 3rdPty bit is set, in which case this field specifies the SCSI ID (0

 

through 7 only) of the initiator to be granted the reservation of the logical unit. The drive preserves the

 

reservation until one of the following occurs:

Third

• It is superseded by another valid RESERVE command from the initiator.

• It is released by the same initiator

Party

• It is released by a TARGET RESET message from any initiator.

Device ID

• It is released by a hard reset condition.

 

The drive ignores any attempt to release the reservation made by any other initiator. For example, if

 

ID7 sends ID2 a Third Party reservation on behalf of ID6 (the target at ID2 gets reserved for the initiator

 

ID6), then only ID7 can release the target at ID2 (using a Third Party release). ID6 cannot release the

 

reservation even though the reservation was made on its behalf.

Extent

The drive supports reservations only on entire logical units. The value must be 0.

 

 

Reserva-

Any value in this field is ignored by the drive.

tion Identi-

fication

 

Extent List

Any value in this field is ignored by the drive.

Length

 

Note: The drive returns RESERVATION CONFLICT status if the unit is already reserved for another initiator. Once the reservation is honored, any command from another initiator (except INQUIRY or REQUEST SENSE) is rejected with RESERVATION CONFLICT status.

Maxtor Atlas 10K V

5-135

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Maxtor 10K V manual Reserve 6 Command 16h, 180RESERVE 6 Command Descriptor Block-Data Format