Dell PowerVault ML6000 Dell PowerVault ML6000 SCSI Reference Guide - Page 68

Read Element Status – B8h, What the Library Does With This Command, Command Usage

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Read Element Status - B8h What the Library Does With This Command The library returns current status and information regarding the requested elements. The data is primarily derived from having done an Inventory operation (using INITIALIZE ELEMENT STATUS or INITIALIZE ELEMENT STATUS WITH RANGE), but in the case of data transfer elements is also augmented by communication with the drives. Element status remains valid as long as the subsystem integrity has not been breached, such as by opening a door or through a power cycle. Element status will be reported for all elements, including those represented by only a placeholder, as in the case of uninstalled drives or magazines that physically have a place reserved in the configuration. As such, it is important to process the fields governing accessibility and exception conditions. Command Usage This command should be issued whenever new element status information is needed, or the library has indicated that status may have changed. If the status information is suspect, an INITIALIZE ELEMENT STATUS WITH RANGE command should be issued to refresh it. Read Element Status CDB Format The READ ELEMENT STATUS CDB format is shown in the following table. Table 57 READ ELEMENT STATUS CDB format Byte Bit 7 6 5 4 3 2 1 0 0 Op Code (B8h) 1 Logical Unit Number VolTag Element Type Code 2 Starting Element Address 3 4 Number of Elements 5 6 Reserved CurDat DVCID a 7 Allocation Length 9 10 Reserved 11 Control Volume Tag (VolTag) - This field indicates whether the volume tag (bar code label) information should be returned. A value of one will return the labels, a value of zero will not. 58 SCSI Commands

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58
SCSI Commands
Read Element Status – B8h
What the Library Does With This Command
The library returns current status and information regarding the requested elements. The data is primarily
derived from having done an Inventory operation (using INITIALIZE ELEMENT STATUS or INITIALIZE
ELEMENT STATUS WITH RANGE), but in the case of data transfer elements is also augmented by
communication with the drives. Element status remains valid as long as the subsystem integrity has not
been breached, such as by opening a door or through a power cycle.
Element status will be reported for all elements, including those represented by only a placeholder, as in the
case of uninstalled drives or magazines that physically have a place reserved in the configuration. As such,
it is important to process the fields governing accessibility and exception conditions.
Command Usage
This command should be issued whenever new element status information is needed, or the library has
indicated that status may have changed. If the status information is suspect, an INITIALIZE ELEMENT
STATUS WITH RANGE command should be issued to refresh it.
Read Element Status CDB Format
The READ ELEMENT STATUS CDB format is shown in the following table.
Volume Tag (VolTag)
– This field indicates whether the volume tag (bar code label) information should be
returned. A value of one will return the labels, a value of zero will not.
Table 57
READ ELEMENT STATUS CDB format
Bit
Byte
7
6
5
4
3
2
1
0
0
Op Code (B8h)
1
Logical Unit Number
VolTag
Element Type Code
2
Starting Element Address
3
4
Number of Elements
5
6
Reserved
CurDat
a
DVCID
7
Allocation Length
9
10
Reserved
11
Control