Read Element Status - B8h

The READ ELEMENT STATUS CDB format is shown in the following table.

Table 1: 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	Starting Element Address
4	Number of Elements
5	Number of Elements
6	Reserved						CurData	DVCID
7 : 9	Allocation Length
7 : 9	Allocation Length
10	Reserved
11	Control

Field	Description
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.
Element Type Code	This field specifies the element types selected for the returned information, as shown in Table 2.
Starting Element Address	This field specifies the minimum element address to report. Only elements with an element type code specified by the Element Type Code field, and with an address greater than or equal to the starting element address will be reported. The starting element address must be a valid element address, but not have to be within the range specified by the Element Type Code field.
Number of Elements	This field specifies the maximum number of element descriptors to return. Only those descriptors that can be completely transferred within the allotted allocation length will be returned.
Current Data (CurData)	This field specifies whether the library may cause device motion to confirm element status data. The library will not cause device motion if this field is set to either 0 or 1.
Device ID (DVCID)	This field indicates whether device identifiers (inquiry page information or serial numbers) are returned for the specified range. Identifiers are returned if this field is set to 1. They are not returned if this field is set to 0. Only data transfer elements can return device identifiers.
Allocation Length	This field specifies the byte length allowed for returned element descriptors. Only complete element descriptors are returned. The library returns element descriptors until one of the following conditions are met: All available element descriptors have been returned The number of element descriptors specified in the Number of Elements field have been returned The number of bytes specified in the Allocation Length field have been returned There is less allocation length space available than is required by the next complete element descripto

Table 2: Element Type Code

Code	Selected Element Type
0000b (0)	All element types reported
0001b (1)	Medium transport element (accessor)
0010b (2)	Storage element
0011b (3)	Import/Export element
0100b (4)	Data transfer element (drives)

Read Element Status Response

Element status data consists of an eight-byte header, followed by one or more element status pages (per element type). Each element status page consists of a header, followed by one or more element descriptor blocks. A complete response then looks like:

Element Status Header

Element Status Page Header (first element type)

Element Descriptor

…(more descriptors)…

Element Descriptor

…(more status pages)…

Element Status Page Header (next element type)

Element Descriptor

…

Element Descriptor

There are only up to four Element Status Pages, one for each element type.

Element Status Header

One header is returned for each READ ELEMENT STATUS command. The format is shown in the following table.

Table 3: Element Status Header format

Bit Byte	7	6	5	4	3	2	1	0
0	First Element Address Reported
1	First Element Address Reported
2	Number of Elements Available
3	Number of Elements Available
4	Reserved
5 : 7	Byte Count of Report Available
5 : 7	Byte Count of Report Available

Field	Description
First Element Address Reported	This field indicates the lowest element address found that meets the CDB request.
Number of Elements Available	This field indicates the number of elements found that meet the CDB request.
Byte Count of Report Available	This field indicates the number of available element status bytes that meet the CDB requirements. The value does not include the eight-byte element status header, and is not adjusted to match the value specified in the Allocation Length field of the CDB. This facilitates first issuing a READ ELEMENT STATUS command with an allocation length of eight bytes in order to determine the allocation length required to transfer all the element status data specified by the command.

Element Status Page

Each element status page consists of an eight-byte header, followed by one or more element descriptor blocks. One Element Status Page header is returned for each grouping of element descriptor blocks, by element type. The format of the Element Status Page header is shown in the following table.

Table 4: Element Status Page

Bit Byte	7	6	5	4	3	2	1	0
0	Element Type Code
1	PVolTag	AVolTag	Reserved
2	Element Descriptor Length
3	Element Descriptor Length
4	Reserved
5 : 7	Byte Count of Descriptor Data Available
5 : 7	Byte Count of Descriptor Data Available

Field	Description
Element Type Code	This field indicates the specific element type being returned by the element descriptors for this page.
PVolTag	A value of one indicates that the primary volume tag field (barcode label) is present in each of the element descriptor blocks that follow. A value of zero indicates that they are not present.
AVolTag	Alternate Volume Tags are not supported. The returned value for this field is 0, and the alternate volume tag fields are omitted from the element descriptors.
Element Descriptor Length	This field indicates the number of bytes contained in a single element descriptor. Refer to the individual element descriptor descriptions for each element type for their respective possible lengths.
Byte Count of Descriptor Data Available	This field indicates the number of element descriptor data bytes available for the elements of this element type that meet the CDB requirements. This value represents the Element Descriptor Length field multiplied by the number of element descriptors for this element type. This value does not include the 8-byte Element Status Page header, nor is it adjusted to match the allocation length.

Element Descriptors

The following sections contain the definitions for the following element descriptors:

Medium transport element
Storage elements
Import/Export elements
Data transfer elements

Each element descriptor includes the element address, status flags, source storage element address, and barcode label. Some descriptors also contain extended status information. Additional sense code and qualifier information depends on the element type.

Primary Volume Tag Field

Volume tags (returned in the Primary Volume Tag field) are basically barcode labels on the media. The library supports labels from 5 to 16 characters in length. The Primary Volume Tag field contains 32 bytes of label data (space filled to 32 bytes), followed by two reserved bytes, then two bytes of volume sequence number. The library returns zeros for the last four bytes of Primary Volume Tag data.

If the user has configured the library to support media identification, media identifiers will be reported as configured per partition barcode reporting setting.

Medium Transport Element Descriptor

Table 5: Primary Volume Tag Field

Bit Byte	7	6	5	4	3	2	1	0
0	Element Address
1	Element Address
2	Element Descriptor Length					Except	Rsvd	Full
3	Reserved
4	Additional Sense Code
5	Additional Sense Code Qualifier
6 : 8	Reserved
6 : 8	Reserved
9	Svalid	Invert	Reserved
10	Source Storage Element Address
11	Source Storage Element Address
12 : 47	Primary Volume Tag Information (Field omitted if PVolTag = 0; remaining fields move up)
12 : 47
48 : 51	Reserved
48 : 51	Reserved

Field	Description
Element Address	This field contains the element address of the medium transport.
Except	This field is set to 1 if the element is in an abnormal state. Additional information will be available in the Additional Sense Code and Additional Sense Code Qualifier fields. This field is set to 0 if the element is in a normal state.
Full	This field is set to 0 if the element does not contain media. It is set to 1 if it does. Since the medium transport element cannot be a destination element, this field should normally return 0. There may be error situations where media is left in the picker, which would be indicated by this field. In the case of dual pickers, differentiation of state will be provided through the Additional Sense Code and Additional Sense Code Qualifier fields when exception conditions are present (such as stranded media). Note: Since the medium transport element is virtualized, any media being transported will not be reported doing a move operation and will be reported in either its source or destination element while being moved.
Additional Sense Code	If the element is in an abnormal state (an exception associated with it), this field will be set to a value as described in Table 4.
Additional Sense Code Qualifier	If the element is in an abnormal state, this field will be set to a value as described in Table 4.
Source Valid (Svalid)	This field is set to 1 if the Source Storage Element Address field is valid, otherwise it is set to 0. Note: Since the medium transport element is virtualized, any media being transported will not be reported doing a move operation and will be reported in either its source or destination element while being moved.
Invert	This field is set to 0. The library does not support inverting media.
Source Storage Element Address	If the Source Valid field is set to 1, this field will contain the element address of the last storage element the media was in. Since the medium transport element cannot be a destination element, this would be an abnormal condition. Note: Since the medium transport element is virtualized, any media being transported will not be reported doing a move operation and will be reported in either its source or destination element while being moved.
Primary Volume Tag	This field will normally return spaces if the primary volume tag is requested, since the medium transport element is virtualized. In certain error situations, a volume tag will be returned to indicate which cartridge may be stranded within the picker. Note: Since the medium transport element is virtualized, any media being transported will not be reported doing a move operation and will be reported in either its source or destination element while being moved.

Storage Element Descriptor

Table 6: Storage Element Descriptor

Bit Byte	7	6	5	4	3	2	1	0
0	Element Address
1	Element Address
2	Reserved				Access	Except	Rsvd	Full
3	Reserved
4	Additional Sense Code
5	Additional Sense Code Qualifier
6 : 8	Reserved
6 : 8	Reserved
9	Svalid	Invert	Reserved
10	Source Storage Element Address
11	Source Storage Element Address
12 : 47	Primary Volume Tag Information (Field omitted if PVolTag = 0; remaining fields move up)
12 : 47
48 : 51	Reserved
48 : 51	Reserved

Field	Description
Element Address	This field contains the element address of the storage element.
Access	This field is set to 1 if access by a medium transport element is allowed. It is set to 0 if access is denied.
Except	This field is set to 1 if the element is in an abnormal state. Additional information may be available in the Additional Sense Code and Additional Sense Code Qualifier fields. If this field is 1, the primary volume tag information could be invalid. This field is set to 0 if the element is in a normal state.
Full	This field is set to 0 if the element does not contain media. It is set to 1 if it does.
Additional Sense Code	If the element is in an abnormal state, this field will be set to a value as described in Table 4.
Additional Sense Code Qualifier	If the element is in an abnormal state, this field will be set to a value as described in Table 4.
Source Valid (Svalid)	This field is set to 1 if the Source Storage Element Address (media home slot) field is valid, otherwise it is set to 0.
Invert	This field is set to 0. The library does not support inverting media.
Source Storage Element Address	If the Source Valid field is set to 1, this field will contain the element address of the last storage element the media was moved from. It may be the same as this element.
Primary Volume Tag	If requested, this field contains the volume tag (bar code label) information for media residing in this element address.

Import/Export Element Descriptor

Table 7: Import/Export Element Descriptor

Bit Byte	7	6	5	4	3	2	1	0
0	Element Address
1	Element Address
2	Reserved		InEnab	ExEnab	Access	Except	Imp/Exp	Full
3	Reserved
4	Additional Sense Code
5	Additional Sense Code Qualifier
6 : 8	Reserved
6 : 8	Reserved
9	Svalid	Invert	Reserved
10	Source Storage Element Address
11	Source Storage Element Address
12 : 47	Primary Volume Tag Information (Field omitted if PVolTag = 0; remaining fields move up)
12 : 47
48 : 51	Reserved
48 : 51	Reserved

All fields are the same as for the Storage Element Descriptor except:

Field	Description
Element Address	This field contains the element address of the import/export element.
Import Enable (InEnab)	A value of one indicates that the element supports movement of media into the scope of the media changer device. A value of zero indicates that this element does not support import actions. The library returns a value of one for all import/export elements.
Access	This field is set to 1 if access by a medium transport element is allowed. It is set to 0 if access is denied.
Except	This field is set to 1 if the element is in an abnormal state. Additional information may be available in the Additional Sense Code and Additional Sense Code Qualifier fields. If this field is 1, the primary volume tag information could be invalid. This field is set to 0 if the element is in a normal state.
Export Enable (ExEnab)	A value of one indicates that the element supports movement of media out of the scope of the media changer device. A value of zero indicates that this element does not support export actions. The library returns a value of one for all import/export elements.
Import/Export (ImpExp)	A value of one indicates that media present in the element was placed there by an operator. A value of zero indicates that media present in the element was placed there by a medium transport element.
Full	This field is set to 0 if the element does not contain media. It is set to 1 if it does.
Additional Sense Code	If the element is in an abnormal state, this field will be set to a value as described in Table 4.
Additional Sense Code Qualifier	If the element is in an abnormal state, this field will be set to a value as described in Table 4.
Source Valid (Svalid)	This field is set to 1 if the Source Storage Element Address (media home slot) field is valid, otherwise it is set to 0.
Invert	This field is set to 0. The library does not support inverting media.
Source Storage Element Address	If the Source Valid field is set to 1, this field will contain the element address of the last storage element the media was moved from. It may be the same as this element.
Primary Volume Tag	If requested, this field contains the volume tag (bar code label) information for media residing in this element address.

Data Transfer Element Descriptor

Table 8: Data Transfer Element Descriptor

Bit Byte	7	6	5	4	3	2	1	0
0	Element Address
1	Element Address
2	Reserved				Access	Except	Rsvd	Full
3	Reserved
4	Additional Sense Code
5	Additional Sense Code Qualifier
6	NotBus	Rsvd	IDValid	LUValid	Rsvd	Logical Unit Number
7	SCSI Bus Address
8	Reserved
9	SValid	Invert	Reserved
10	Source Element Address
11	Source Element Address
12 : 47	Primary Volume Tag Information (Field omitted if PVolTag = 0; remaining fields move up)
12 : 47
48	Reserved				Code Set
49	Reserved				Identifier Type
50	Reserved
51	Identifier Length = x where x is 0h to 40h (valid identifier data)
52 : 115	Device Identifier (Field omitted if DVCID = 0, remaining fields move up) (Always padded to 64 byte length if DVCID = 1)
52 : 115

Field	Description
Element Address	This field contains the element address of the data transfer element.
Access	This field is set to 1 if access by a medium transport element is allowed. It is set to 0 if access is denied. When set to 1, it implies that cartridges are unloaded and accessible if present. When set to 0, it implies that cartridges are not unloaded if present.
Except	This field is set to 1 if the element is in an abnormal state. Additional information may be available in the Additional Sense Code and Additional Sense Code Qualifier fields. If this field is 1, the primary volume tag information could be invalid. This field is set to 0 if the element is in a normal state.
Full	This field is set to 0 if the element does not contain media. It is set to 1 if it does.
Additional Sense Code	If the element is in an abnormal state, this field will be set to a value as described in “Additional Sense Codes and Qualifiers.”
Additional Sense Code Qualifier	If the element is in an abnormal state, this field will be set to a value as described in “Additional Sense Codes and Qualifiers.”
Not This Bus (NotBus)	This field is not supported and is set to 0.
IDValid	A value of one indicates that the SCSI Bus Address field is valid. A value of zero indicates that it is not.
LUValid	This field is not supported and is set to 0.
Logical Unit Number	This field is not supported and is set to 0.
SCSI Bus Address	When the IDValid field is set to one, this field contains the tape drive SCSI address. This is only applicable to SCSI tape drives, and does not apply to Fibre Channel tape drives.
Source Valid (Svalid)	This field is set to 1 if the Source Storage Element Address (media home slot) field is valid, otherwise it is set to 0.
Invert	This field is set to 0. The library does not support inverting media.
Source Storage Element Address	If the Source Valid field is set to 1, this field will contain the element address of the last storage element the media was moved from.
Primary Volume Tag	If requested, this field contains the volume tag (bar code label) information for media residing in this element address.
Code Set	This field is set to: 0h – RESERVED. 1h – The device identifier field contains binary values. 2h – The device identifier field contains ASCII values.
Identifier Type	This field is set to: 0h – The Device Identifier, if the Identifier Length is set, lists the vendor specific device serial number only. 1h – The Device Identifier lists the eight-byte Vendor Identification, followed by vendor specific unique identifier information. 2h – The Device Identifier contains a Canonical form of IEEE Extended Unique Identifier, 64-bit (EUI-64). In this case, the Identifier Length field is set to 8. 3h – The Device Identifier contains an FC-PH Name_identifier.
Identifier Length	This field contains the length in bytes of valid Device Identifier information. If no device identifier is available, or the DVCID bit in the CDB is zero, the Identifier Length field is 0h and the Code Set and Identifier Type fields are also 0h. If the DCVID bit is set, the Identifier Length may be set between 0 and 64 (40h) bytes, depending on the associated identifier type.
Device Identifier	This field provides up to 64 bytes of device identifier information for the device associated with the data transfer element. If the Identifier Type 1 is specified, drive’s Inquiry page 83h is reported. The Identifier Length specifies the length of valid device identifier information. If the DVCID bit in the CDB is zero, this field is omitted and padded with with ASCII character 20h (space) to fill the complete 64 bytes. If the DVCID bit is set and the Identifier Length is 0, this field will still be 64 bytes long.