User's Guide

Quantum Scalar Intelligent Libraries SCSI Reference Guide Guide 51
Read Reservations Response
The response for a Read Reservations service action is shown in the following table.
Generation – This field is a 32-bit counter that is incremented every time a PERSISTENT RESERVE OUT
command requests a Register, a Register and Ignore Existing Key, a Clear, a Preempt, or a Preempt and
Abort service action. This counter is not maintained across power cycles.
Additional Length – This field indicates the length in bytes of the Reservation Descriptor, which may return
0 or 0010h (16).
Since element reservations are not supported, a single reservation descriptor is returned for logical unit.
Reservation Key – This is the 8-byte reservation key that was registered through the PERSISTENT
RESERVE OUT command.
Scope-Specific Address – Element reservations are not supported and this field returns 0000h.
Scope – This field returns a 0h, indicating logical unit scope. Element scope is not supported.
Type – This field returns the type of reservation as follows:
• 3h Exclusive Access – The initiator holding the persistent reservation has exclusive read and write
access. Requests from any other initiators to transfer data to or from the logical unit will result in a
Reservation Conflict.
• 6h Exclusive Access, Registrants Only – Any currently registered initiator has exclusive data
transfer access. Requests from unregistered initiators to transfer data to or from the logical unit will
result in a Reservation Conflict.
• 8h Exclusive Access, All Registrants (only supported if the command is issued to a Media Changer
hosted by an HP tape drive).
Table 47 Read Reservations Response
Bit
Byte
76543210
0
:
3
Generation
4
:
7
Additional Length (0 or 0010h)
Reservation Descriptor
8
:
15
Reservation Key
16
:
19
Scope-Specific Address
20 Reserved
21 Scope Type
22
Obsolete
23