Quantum 1200 Series DAT Autochanger Betriebsanweisung PDF herunterladen (Seite 181)

SDLT 600 SCSI Interface Guide Chapter 4: SCSI Commands

81-81200-02 REV A01 January 2005 4-139

The figure and table below illustrate and describe the data fields of each Read Reservations

descriptor’s data fields.

Table 4-79. Read Reservations Parameters — Field Descriptions

Field Name Description

PRGeneration Persistent Reservations Generation. The value in this field is a 32-bit counter in

the drive that is incremented each time a PERSISTENT RESERVE OUT

command requests a Register, Clear, Pre-empt, or Pre-empt & Clear operation.

Note that PERSISTENT RESERVE IN commands do not increment the

counter, nor do PERSISTENT RESERVE OUT commands that perform a

Reserve or Release service action, or that are not performed due to an error or a

reservation conflict. The value in the Generation field is set to 0 as part of the

power-on self test process.

The value in the Generation field allows the application client that examines the

value to verify that another application client has not modified the configuration

of the initiators attached to a logical unit without notifying the application client

doing the examination.

Additional

Length

Contains the count of the number of bytes that are in the Read Reservation

descriptors (bytes 8 – n). Note that this field contains the number of bytes

regardless of the value prescribed by the Allocation Length field in the

command’s CDB.

Reservation

Descriptors

The drive reports one Reservation descriptor for each unique persistent

reservation on the logical unit when the PERSISTENT RESERVE IN command

has indicated a Read Reservations action. Figure 4-79 on page 4-140 and

Table 4-80 on page 4-140 contain details about the contents of each Reservation

Descriptors field.

Bit

Byte

7 6 5 4 3 2 1 0

0 – 7

(MSB)

Reservation Key

(LSB)

8 – 11

(MSB)

Scope-Specific Address

(LSB)

12 Reserved

13 Scope Type

14 – 15 Obsolete

1 2 ... 176 177 178 179 180 181 182 183 184 185 186 ... 293 294

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