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16. Medium-Changer Devices
16.1. Medium-Changer Device Model
Medium changer devices mechanize the movement of media to and from primary
devices (such as disk or tape drives) and other locations within the range of
the medium changer. The medium changer command set is based on a physical
model of this functionality.
This command set supports varied physical implementations of the medium
changer function. Most of these variations are hidden from the initiator by
the high level of function provided by the MOVE MEDIUM and EXCHANGE MEDIUM
commands and by the generalized nature of the element addressing scheme.
However, initiators may need to be aware of the capabilities of the particular
medium changer device. These characteristics and capabilities are conveyed via
MODE SENSE pages.
16.1.1. Medium-Changer Elements
The medium-changer command set uses as its address space the set of physical
locations and mechanisms within the scope of a medium changer device. The term
element is used throughout this section to refer to one member of the medium
changer address space. Each element is a discrete physical entity that may
hold zero or one physical unit of media - one disk cartridge, one spool of
tape, etc. Element addresses do not extend across multiple physical units of
media. Likewise, element addresses are independent of any logical partitioning
that the primary device may support within a physical unit of media.
A medium changer is viewed as a set of addressable elements, each of which
may contain a unit of media or be used to move a unit of media. Each medium
changer element has a unique 16 bit element address. Each element is an
instance of one of four classes or element types.
1. MEDIUM TRANSPORT ELEMENT
2. STORAGE ELEMENT
3. IMPORT EXPORT ELEMENT
4. DATA TRANSFER ELEMENT
Units of media (cartridges, cassettes, caddies, etc.) are referred to only
indirectly by this device model. Units of media can be moved to or from any
of the elements of the medium changer device. The presence of media at the
various elements in a medium changer can be sensed. In order to ensure
exclusive access to a unit of media, the element where the unit of media is
located (the element address) must be reserved.
Elements of the medium transport, import export and (rarely) data transport
types may not provide independent storage for medium. The capabilities of a
particular medium changer in this respect can be sensed via the device
capabilities page of the Mode Sense data. The following hypothetical medium
changer implementation illustrates one case of an element not providing
independent storage for medium. Consider a medium changer which has a
carousel style storage for medium. The import export function could be
provided by a port which allows operator access to one of the storage
elements. In such a device, the MOVE ELEMENT command from storage element to
import export element would rotate the carousel to align the addressed storage
element to the import export position. In this case the import export element
does not provide independent storage but rather access to one of the storage
elements.
16.1.1.1. Medium Transport Elements
Medium transport elements address the functions of the medium changer device
that perform the movement of units of media. Where a medium transport element
can serve (even temporarily) as a storage location for medium, the location of
each unit of media must have a separate element address.
In larger medium changer devices, the medium movement functions may be
performed by multiple independent robotic subsystems. Each of these may have a
number of medium transport element addresses. The element addresses within
each subsystem shall be contiguous. Any of the element addresses within a
subsystem may be used interchangeably in the medium transport element address
field of MOVE MEDIUM and EXCHANGE MEDIUM commands. An initiator may determine
the capabilities of the medium movement facilities of a medium changer device
via the transport geometry MODE SENSE page, 16.3.3.3.
Element address zero is reserved for use in the medium transport element
address field of MOVE MEDIUM and EXCHANGE MEDIUM commands to direct the medium
changer to use a default or medium changer selected medium transport element.
In some implementations, medium transport elements may be source and/or
destination addresses in MOVE MEDIUM and EXCHANGE MEDIUM commands. They may
or may not provide independent storage of a unit of media. See the device
capabilities MODE SENSE page, 16.3.3.
16.1.1.2. Storage Elements
Storage elements are locations of units of media while not in some other
element type. Medium in storage elements is available for access by medium
transport elements.
Storage elements may be source and/or destination addresses in MOVE MEDIUM
and EXCHANGE MEDIUM commands.
16.1.1.3. Import Export Elements
Import export elements are locations of units of media which are being
inserted into or withdrawn from the medium changer device. Medium in these
elements is accessible by both medium transport elements, by the operator, or
by another independent medium changer device.
Import export elements may be source and/or destination addresses in MOVE
MEDIUM and EXCHANGE MEDIUM commands. They may or may not provide independent
storage of a unit of media, see the device capabilities MODE SENSE page,
16.3.3.
Particular import export elements may be capable of either import actions,
export actions, both or neither (if an element is not present).
16.1.1.4. Data Transfer Element
Data transfer elements are locations of the primary devices which are
capable of reading or writing the medium. Data transfer elements may also be
viewed as medium changer element addresses of units of media loaded in or
available for loading in or removal from primary devices such as disk or tape
drives. Note that the medium changer function specified in this section does
not control the primary device. That is the responsibility of the system.
Data transfer elements may be source and/or destination addresses in MOVE
MEDIUM and EXCHANGE MEDIUM commands. They may or may not provide independent
storage of a unit of media, see the device capabilities MODE SENSE page,
16.3.3.
16.1.2. SCSI Addressing of Medium Changer Devices
Medium Changer devices respond to a SCSI ID / LUN address different from
those used by the data transfer element devices. If the data transfer
elements served by the medium changer device are SCSI devices, they may be
addressed though the same SCSI ID as the changer device but with a different
logical unit number or through a different SCSI ID. There is no requirement
that communication with the data transfer elements be done with the same SCSI
bus as the medium changer device or by an SCSI interface at all. This command
set does not support addressing both the changer and the data transfer
elements with the same SCSI ID / LUN because the device at a particular SCSI
ID / LUN address must have a single peripheral device type.
The READ ELEMENT STATUS response page for data transfer elements provides
the SCSI ID / LUN address of the primary devices serviced by a medium changer
device if known to the medium changer device.
16.1.3. Data Access Operations Using a Medium Changer Device
The medium changer device moves units of media among the several elements
accessible to it. It is able to report the full/empty status of any of these
elements. Data transfer elements represent the interface between the medium
changer device and some primary device such as a removable media optical disk
drive or tape drive.
In order to access data on a unit of media currently located in a medium
changer storage element, a system will have to issue commands to both the
medium changer device and to the primary device. The commands to the medium
changer may include MOVE MEDIUM or EXCHANGE MEDIUM plus READ ELEMENT STATUS
commands. The commands to the primary device may include TEST UNIT READY,
INQUIRY, START STOP and LOAD UNLOAD commands in addition to READ and WRITE
commands.
16.1.4. Element Status Maintenance Requirements
If the medium changer device chooses to implement the READ ELEMENT STATUS
command, the medium changer device must be capable of reporting the various
data (i.e. full, error, etc.) required by each page type. The medium changer
may maintain this information at all times or regenerate it in response to the
READ ELEMENT STATUS command. The INITIALIZE ELEMENT STATUS command can be used
to force regeneration of this information.
16.1.5. Volume Tags
The Read Element Status descriptor format for all element types includes two
sets of fields that contain volume tag information. These optional fields are
used to report media identification information that the medium changer has
acquired either by reading an external label (e.g. bar code labels), by a SEND
VOLUME TAG command or by other means which may be vendor unique. The same
volume tag information shall be available to all initiators whether assigned
by that initiator, by some other initiator or by the media changer itself.
Volume tag information provides a means to confirm the identity of a unit of
media that resides in a medium changer element. This command set does not
define any direct addressing of units of media based on these fields. However,
commands are defined that provide translation between volume tag information
and the element address where that unit of media currently resides.
The medium changer command set definition does not impose the requirement
that volume tag information be unique over the units of media within the scope
of the changer device.
The following commands support the optional volume tag functionality:
(1) SEND VOLUME TAG - either as a translation request or to associate a
Volume Tag with the unit of media currently residing at an element address.
(2) REQUEST VOLUME ELEMENT ADDRESS - return the element address currently
associated with the volume tag information transferred with the last Send
Volume Tag command.
(3) READ ELEMENT STATUS - optionally reports volume tag information for all
element types.
(4) MOVE MEDIUM and EXCHANGE MEDIUM commands - if volume tags are
implemented, these commands must retain the association between volume tag
information and units of media as they are moved from element to element.
16.1.5.1. Volume Tag Format
Volume tag information consists of a volume identifier field of 32 bytes
plus a volume sequence number field of 2 bytes. The volume identifier shall
consist of a left justified sequence of ASCII characters. Unused positions
shall be blank (20h) filled. In order for the SEND VOLUME TAG translate with
template to work the characters '*' and'?' (2Ah and 3Fh) must not appear in
volume identification data and there must be no blanks (20h) within the
significant part of the volume identifier. If volume tag information for a
particular element is undefined, the volume identifier field shall be zero.
The volume sequence number is a 2 byte integer field. If the volume sequence
number is not used this field shall be zero. The volume tag contents are
independent of the volume identification information recorded on the media.
IMPLEMENTORS NOTE: For compatibility with the volume identifier defined by
volume and file structure standards, it is recommended that the characters
in the significant non-blank portion of the volume identifier field be
restricted to the set: '0'..'9', 'A'..'Z', and '_' (30h .. 39h, 41h .. 5Ah,
5Fh). Specific systems may have differing requirements that may take
precedence over this recommendation.
Table 16-1 defines the fields within the 36 byte primary and alternate
volume tag information fields found in READ ELEMENT STATUS descriptors and in
the data format for the SEND VOLUME TAG command.
Table 16-1: Volume Tag Information Format
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | |
- - -|- - - Volume Identification Field - - -|
31 | |
-----|-----------------------------------------------------------------------|
32 | |
- - -|- - - Reserved - - -|
33 | |
-----|-----------------------------------------------------------------------|
34 | (MSB) |
-----|--- Volume Sequence Number ---|
35 | (LSB) |
==============================================================================
16.1.5.2. Primary and Alternate Volume Tag Information
Element status descriptors as reported by the READ ELEMENT STATUS command
define a primary volume tag and an alternate volume tag. Alternate volume tag
information provides a means for a system to use different volume
identification information for each side of double sided media. In such a
system, the primary volume tag information refers to the logical medium
accessible via a MOVE MEDIUM command without the invert bit set. The alternate
volume tag information refers to the other side of the media, i.e. the side
that would be accessed via a MOVE MEDIUM command with the invert bit set.
16.2. Commands for Medium Changer Devices
The commands for medium changer devices shall be as shown in Table 16-2.
Table 16-2: Commands for Medium Changer Devices
==============================================================================
Operation
Command Name Code Type Section
------------------------------------------------------------------------------
CHANGE DEFINITION 40h O 7.2.1
EXCHANGE MEDIUM A6h O 16.2.1
INITIALIZE ELEMENT STATUS 07h O 16.2.2
INQUIRY 12h M 7.2.5
LOG SELECT 4Ch O 7.2.6
LOG SENSE 4Dh O 7.2.7
MODE SELECT(6) 15h O 7.2.8
MODE SELECT(10) 55h O 7.2.9
MODE SENSE(6) 1Ah O 7.2.10
MODE SENSE(10) 5Ah O 7.2.11
MOVE MEDIUM A5h M 16.2.3
POSITION TO ELEMENT 2Bh O 16.2.4
PREVENT ALLOW MEDIUM REMOVAL 1Eh O 8.2.4
READ BUFFER 3Ch O 7.2.12
READ ELEMENT STATUS B8h O 16.2.5
RECEIVE DIAGNOSTIC RESULTS 1Ch O 7.2.13
RELEASE 17h O 16.2.6
REQUEST VOLUME ELEMENT ADDRESS B5h O 16.2.7
REQUEST SENSE 03h M 7.2.14
RESERVE 16h O 16.2.8
REZERO UNIT 01h O 8.2.13
SEND DIAGNOSTIC 1Dh M 7.2.15
SEND VOLUME TAG B6h O 16.2.9
TEST UNIT READY 00h M 7.2.16
WRITE BUFFER 3Bh O 7.2.17
==============================================================================
Key: M = Command implementation is mandatory.
O = Command implementation is optional.
Operation codes C0h through FFh are vendor specific. All other operation
codes are reserved.
16.2.1. EXCHANGE MEDIUM Command
Table 16-3: EXCHANGE MEDIUM Command
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | Operation Code (A6h) |
-----|-----------------------------------------------------------------------|
1 | Logical Unit Number | Reserved |
-----|-----------------------------------------------------------------------|
2 | (MSB) |
-----|--- Transport Element Address ---|
3 | (LSB) |
-----|-----------------------------------------------------------------------|
4 | (MSB) |
-----|--- Source Address ---|
5 | (LSB) |
-----|-----------------------------------------------------------------------|
6 | (MSB) |
-----|--- First Destination Address ---|
7 | (LSB) |
-----|-----------------------------------------------------------------------|
8 | (MSB) |
-----|--- Second Destination Address ---|
9 | (LSB) |
-----|-----------------------------------------------------------------------|
10 | Reserved | Inv2 | Inv1 |
-----|-----------------------------------------------------------------------|
11 | Control |
==============================================================================
The EXCHANGE MEDIUM command (Table 16-3) provides a means to exchange the
medium in the source element with the medium located at a destination element.
IMPLEMENTORS NOTE: Support of this command requires that the device have
the capability of handling two units of media at the same time or that it
emulate this capability.
The medium in the source element is moved to the destination 1 element and
the medium which previously occupied the destination 1 element is moved to the
destination 2 element. The destination 2 element may or may not be the same
element as the source element. In the case of a simple exchange, the source
element and the destination 2 element are the same.
If this command is received and the source element is empty or the
destination 1 element is empty or the destination 2 element (if different from
the source element) is full or the destination 2 element (if the same as the
source element) is empty, the target shall return CHECK CONDITION status and
set the sense key to ILLEGAL REQUEST.
The transport element address specifies the medium transport element that is
to be used in executing this command. The default medium transport element
address of zero may be used if this functionality is supported by the medium
changer device. If the address specified has not been assigned or has been
assigned to an element other than a medium transport element, the target shall
return CHECK CONDITION status and the set the sense key to ILLEGAL REQUEST.
The source address, the destination 1 address, and the destination 2 address
may represent a storage element, an import export element, a data transfer
element, or a medium transport element. If the address specified has not been
assigned to a specific element of the medium changer, the target shall return
CHECK CONDITION status and set the sense key to ILLEGAL REQUEST.
The device capabilities MODE SENSE page provides a matrix with the supported
source element / destination 1 element combinations for EXCHANGE MEDIUM
commands with source element the same as destination 2 element. See 16.3.3.
An Inv1 bit of one specifies that the medium shall be inverted prior to
depositing the medium into the destination 1 element.
An Inv2 bit of one specifies that the medium shall be inverted prior to
depositing the medium into the destination 2 element.
If the medium changer does not support medium rotation for handling double
sided media, the Inv1 and Inv2 bits should be set to zero. If either of these
bits is nonzero, a target which is not capable of medium rotation shall return
CHECK CONDITION status and set the sense key to ILLEGAL REQUEST.
16.2.2. INITIALIZE ELEMENT STATUS Command
Table 16-4: INITIALIZE ELEMENT STATUS Command
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | Operation Code (07h) |
-----|-----------------------------------------------------------------------|
1 | Logical Unit Number | Reserved |
-----|-----------------------------------------------------------------------|
2 | Reserved |
-----|-----------------------------------------------------------------------|
3 | Reserved |
-----|-----------------------------------------------------------------------|
4 | Reserved |
-----|-----------------------------------------------------------------------|
5 | Control |
==============================================================================
The INITIALIZE ELEMENT STATUS command (Table 16-4) will cause the Medium
Changer to check all elements for medium and any other status relevant to that
element. The intent of this command is to enable the initiator to get a quick
response from a following READ ELEMENT STATUS command. It may be useful to
issue this command after a power failure, or if medium has been changed by an
operator, or if configurations have been changed.
16.2.3. MOVE MEDIUM Command
Table 16-5: MOVE MEDIUM Command
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | Operation Code (A5h) |
-----|-----------------------------------------------------------------------|
1 | Logical Unit Number | Reserved |
-----|-----------------------------------------------------------------------|
2 | (MSB) |
-----|--- Transport Element Address ---|
3 | (LSB) |
-----|-----------------------------------------------------------------------|
4 | (MSB) |
-----|--- Source Address ---|
5 | (LSB) |
-----|-----------------------------------------------------------------------|
6 | (MSB) |
-----|--- Destination Address ---|
7 | (LSB) |
-----|-----------------------------------------------------------------------|
8 | Reserved |
-----|-----------------------------------------------------------------------|
9 | Reserved |
-----|-----------------------------------------------------------------------|
10 | Reserved | Invert |
-----|-----------------------------------------------------------------------|
11 | Control |
==============================================================================
The MOVE MEDIUM command (Table 16-5) requests that the target move a unit of
media from a source element to a destination element.
The source address specifies the location that the medium is taken from, and
the destination address specifies the location that the medium is moved to.
If this command is received and the source element is empty or the
destination element (if different from the source element) is full, the target
shall return CHECK CONDITION status and set the sense key to ILLEGAL REQUEST.
The transport element address specifies the medium transport element that is
to be used in executing this command. The default medium transport element
address of zero may be used if this functionality is supported by the medium
changer device. If the address specified has not been assigned or has been
assigned to an element other than a medium transport element, the target shall
return CHECK CONDITION status and the set the sense key to ILLEGAL REQUEST.
The source address and the destination address may represent a storage
element, an import export element, a data transfer element, or a medium
transport element. If the address specified has not been assigned to a
specific element of the medium changer, the target shall return CHECK
CONDITION status and set the sense key to ILLEGAL REQUEST.
The device capabilities MODE SENSE page provides a matrix with the supported
source element or destination element combinations for the MOVE MEDIUM command.
See 16.3.3.
An invert bit of one specifies that the medium shall be inverted or rotated
prior to depositing the medium into the destination element. If the medium
changer does not support medium rotation for handling double sided media, the
invert bit should be set to zero. If this bit is nonzero, a target which is
not capable of medium rotation shall return CHECK CONDITION status and set the
sense key to ILLEGAL REQUEST.
16.2.4. POSITION TO ELEMENT Command
Table 16-6: POSITION TO ELEMENT Command
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | Operation Code (2Bh) |
-----|-----------------------------------------------------------------------|
1 | Logical Unit Number | Reserved |
-----|-----------------------------------------------------------------------|
2 | (MSB) |
-----|--- Transport Element Address ---|
3 | (LSB) |
-----|-----------------------------------------------------------------------|
4 | (MSB) |
-----|--- Destination Element Address ---|
5 | (LSB) |
-----|-----------------------------------------------------------------------|
6 | Reserved |
-----|-----------------------------------------------------------------------|
7 | Reserved |
-----|-----------------------------------------------------------------------|
8 | Reserved | Invert |
-----|-----------------------------------------------------------------------|
9 | Control |
==============================================================================
The POSITION TO ELEMENT command (Table 16-6) will position the transport
element specified in front of the destination element specified.
IMPLEMENTORS NOTE: In this context, "in front of" is defined to mean --
positioned so that no further motion of the medium transport element is
necessary to execute an appropriate MOVE MEDIUM command between the two
elements.
An invert bit value of one requests that the transport element be inverted
or rotated before positioning in front of the destination element. A value of
zero requests that the orientation be unchanged before positioning in front of
the destination element.
16.2.5. READ ELEMENT STATUS Command
Table 16-7: READ ELEMENT STATUS Command
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | Operation Code (B8h) |
-----|-----------------------------------------------------------------------|
1 | Logical Unit Number | VolTag | Element Type Code |
-----|-----------------------------------------------------------------------|
2 | (MSB) |
-----|--- Starting Element Address ---|
3 | (LSB) |
-----|-----------------------------------------------------------------------|
4 | (MSB) |
-----|--- Number of Elements ---|
5 | (LSB) |
-----|-----------------------------------------------------------------------|
6 | Reserved |
-----|-----------------------------------------------------------------------|
7 | (MSB) |
-----|--- ---|
8 | Allocation Length |
-----|--- ---|
9 | (LSB) |
-----|-----------------------------------------------------------------------|
10 | Reserved |
-----|-----------------------------------------------------------------------|
11 | Control |
==============================================================================
The READ ELEMENT STATUS command (Table 16-7) requests the target report the
status of its internal elements to the initiator.
A volume tag (VolTag) bit of one indicates that the target shall report
volume tag information if this feature is supported. A value of zero indicates
that volume tag information shall not be reported. If the volume tag feature
is not supported this field shall be treated as reserved.
The element type code field specifies the particular element type(s)
selected for reporting by this command. A value of zero specifies that status
for all element types shall be reported. The element type codes are defined
in Table 16-8.
Table 16-8: Element Type Code
==============================================================================
Code Description
----- ---------------------------------------------------
0h All element types reported, (valid in CDB only)
1h Medium Transport Element
2h Storage Element
3h Import Export Element
4h Data Transfer Element
5h-Fh Reserved
==============================================================================
The starting element address specifies the minimum element address to
report. Only elements with an element type code permitted by the element type
code specification and an element address greater than or equal to the
starting element address shall be reported. Element descriptor blocks are not
generated for undefined element addresses.
The number of elements specifies the maximum number of element descriptors
to be created by the target for this command. The value specified by this
field is not the range of element addresses to be considered for reporting but
rather the number of defined elements to report. If the allocation length is
not sufficient to transfer all the element descriptors, the target shall
transfer all those descriptors that can be completely transferred and this
shall not be considered an error.
16.2.5.1. Element Status Data
The data returned by the READ ELEMENT STATUS command shall be as shown in
Tables 16-9 through 16-14 and Figure 16-1. Element status data consists of an
eight-byte header, (Table 16-9) followed by one or more element status pages.
-------------------------------------------------------
| Element Status Data (Table 16-9.) |
| 8 byte header + Element Status Pages |
|-----------------------------------------------------| - - - - - - - - - -
| ------------------------------------------------ | Bytes counted A
| | Element Status Page (Table 16-10.) | | in overall |
| | 8 byte header + Element Descriptors | | header |
| |----------------------------------------------| | - - |
| | ----------------------------------------- | | A |
| | | Element Descriptor (Table 16-11, | | | | Bytes |
| | | 16-12, 16-13 or 16-14.) | | | | counted |
| | ----------------------------------------- | | | in page |
| | ----------------------------------------- | | | header |
| | | Element Descriptor | | | | |
| | ----------------------------------------- | | V |
| ------------------------------------------------ | - - |
| ------------------------------------------------ | |
| | Element Status Page | | |
| |----------------------------------------------| | |
| | ----------------------------------------- | | |
| | | Element Descriptor | | | |
| | ----------------------------------------- | | |
| | . | | |
| | . (More Element Descriptors) | | |
| | . | | |
| ------------------------------------------------ | |
| . | |
| . (More Element Status Pages) | |
| . | V
------------------------------------------------------- - - - - - - - - - -
Figure 16-1: Illustration of Element Status Data Structure
Table 16-9: Element Status Data
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | (MSB) |
-----|--- First Element Address Reported ---|
1 | (LSB) |
-----|-----------------------------------------------------------------------|
2 | (MSB) |
-----|--- Number of Elements Reported ---|
3 | (LSB) |
-----|-----------------------------------------------------------------------|
4 | Reserved |
-----|-----------------------------------------------------------------------|
5 | (MSB) |
-----|--- ---|
6 | Byte Count of Report Available |
-----|--- (all pages, x - 7 ) ---|
7 | (LSB) |
==============================================================================
8 to | |
- - -|- - - Element Status Page(s) - - -|
x | |
==============================================================================
The first element address reported field indicates the element address of
the element with the smallest element address found to meet the CDB request.
The number of elements field indicates the number of elements meeting the
request in the command descriptor block. The status for these elements is
returned if sufficient allocation length was specified.
The byte count of report available field indicates the number of bytes of
element status page data available for all elements meeting the request in the
command descriptor block. This value shall not be adjusted to match the
allocation length available.
IMPLEMENTORS NOTE: The READ ELEMENT STATUS command can be issued 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.
16.2.5.2. Element Status Page
Table 16-10: Element Status Page
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | Element Type Code |
-----|-----------------------------------------------------------------------|
1 | PVolTag| AVolTag| Reserved |
-----|-----------------------------------------------------------------------|
2 | (MSB) |
-----|--- Element Descriptor Length ---|
3 | (z, from tables 16-11 - 16-14.) (LSB) |
-----|-----------------------------------------------------------------------|
4 | Reserved |
-----|-----------------------------------------------------------------------|
5 | (MSB) |
-----|--- ---|
6 | Byte Count of Descriptor Data Available |
-----|--- (this page, y - 7) ---|
7 | (LSB) |
==============================================================================
8 to | |
- - -|- - - Element Descriptor(s) - - -|
y | |
==============================================================================
The element status page is defined in Table 16-9. Each element status page
includes an eight-byte header followed by one or more element descriptor
blocks. The page header (Table 16-10) includes the element type code, the
length of each descriptor block and the number of bytes of element descriptor
information which follow the header for this element type.
The element type code field indicates the element type reported by this
page.
A primary volume tag (PVolTag) bit of one indicates that the primary volume
tag information field is present in each of the following element descriptor
blocks. A value of zero indicates that these bytes are omitted from the
element descriptors that follow.
An alternate volume tag (AVolTag) bit of one indicates that the alternate
volume tag information field is present in each of the following element
descriptor blocks. A value of zero indicates that these bytes are omitted from
the element descriptors that follow.
The element descriptor length field indicates the number of bytes in each
element descriptor.
The byte count of descriptor data available field indicates the number of
bytes of element descriptor data available for elements of this element type
meeting the request in the CDB. This value shall not be adjusted to match the
allocation length available.
Each element descriptor includes the element address, status flags and may
contain sense code information as well as other information depending on the
element type. (Tables 16-11 - 16-14.)
16.2.5.3. Medium Transport Element Descriptor
Table 16-11: Medium Transport Element Descriptor
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | (MSB) |
-----|--- Element Address ---|
1 | (LSB) |
-----|-----------------------------------------------------------------------|
2 | Reserved | Except |Reserved| Full |
-----|-----------------------------------------------------------------------|
3 | Reserved |
-----|-----------------------------------------------------------------------|
4 | Additional Sense Code |
-----|-----------------------------------------------------------------------|
5 | Additional Sense Code Qualifier |
-----|-----------------------------------------------------------------------|
6 | |
- - -|- - - Reserved - - -|
8 | |
-----|-----------------------------------------------------------------------|
9 | SValid | Invert | Reserved |
-----|-----------------------------------------------------------------------|
10 | (MSB) |
-----|--- Source Storage Element Address ---|
11 | (LSB) |
-----|-----------------------------------------------------------------------|
12 | |
- - -|- - - Primary Volume Tag Information - - -|
47 | (Field omitted if PVolTag = 0) |
-----|-----------------------------------------------------------------------|
48 | |
- - -|- - - Alternate Volume Tag Information - - -|
83 | (Field omitted if AVolTag = 0) |
-----|-----------------------------------------------------------------------|
84 | |
- - -|- - - Reserved - - -|
87 | (Field moved up if Volume Tag Information field(s) are omitted.) |
-----|-----------------------------------------------------------------------|
88 | |
- - -|- - - Vendor Unique - - -|
z-1 | (Field moved up if Volume Tag Information field(s) are omitted.) |
==============================================================================
The element address field gives the address of the medium changer element
whose status is reported by this element descriptor block.
An exception (Except) bit of one indicates the element is in an abnormal
state. An exception bit of zero indicates the element is in a normal state.
If this bit is one, information on the abnormal state may be available in the
additional sense code and additional sense code qualifier bytes.
A full bit value of one indicates that the element contains a unit of media.
A value of zero indicates that the element does not contain a unit of media.
The additional sense code field may provide specific information on an
abnormal element state. The values in this field are as defined for the
additional sense code of the REQUEST SENSE data (see Table 7-42).
The additional sense code qualifier field may provide more detailed
information on an abnormal element state. The values in this field are as
defined for the additional sense code qualifier of the REQUEST SENSE data (see
Table 7-42).
A source valid (SValid) bit value of one indicates that the source storage
element address field and the invert bit information is valid. A value of zero
indicates that the values in these fields are not valid.
An invert bit value of one indicates that the unit of media now in this
element was inverted by MOVE MEDIUM or EXCHANGE MEDIUM operations since it was
last in the source storage element. A value of zero indicates that no
inversion occurred during the operation.
The source storage element address field provides the address of the last
storage element this unit of media was moved from. This field is valid only
if the SValid bit is one.
The primary and alternate volume tag information fields provide for
identifying the unit of media residing in this element (see 16.1.5.). Either
or both of these fields may be omitted for all the element descriptor blocks
that comprise an element status page as indicated by the PVolTag and AVolTag
bits in the element status page header (Table 16-10).
16.2.5.4. Storage Element Descriptor
Table 16-12: Storage Element Descriptor
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | (MSB) |
-----|--- Element Address ---|
1 | (LSB) |
-----|-----------------------------------------------------------------------|
2 | Reserved | Access | Except |Reserved| Full |
-----|-----------------------------------------------------------------------|
3 | Reserved |
-----|-----------------------------------------------------------------------|
4 | Additional Sense Code |
-----|-----------------------------------------------------------------------|
5 | Additional Sense Code Qualifier |
-----|-----------------------------------------------------------------------|
6 | |
- - -|- - - Reserved - - -|
8 | |
-----|-----------------------------------------------------------------------|
9 | SValid | Invert | Reserved |
-----|-----------------------------------------------------------------------|
10 | (MSB) |
-----|--- Source Element Address ---|
11 | (LSB) |
-----|-----------------------------------------------------------------------|
12 | |
- - -|- - - Primary Volume Tag Information - - -|
47 | (Field omitted if PVolTag = 0) |
-----|-----------------------------------------------------------------------|
48 | |
- - -|- - - Alternate Volume Tag Information - - -|
83 | (Field omitted if PVolTag = 0) |
-----|-----------------------------------------------------------------------|
84 | |
- - -|- - - Reserved - - -|
87 | (Field moved up if Volume Tag Information field(s) are omitted.) |
-----|-----------------------------------------------------------------------|
88 | |
- - -|- - - Vendor Unique - - -|
z-1 | (Field moved up if Volume Tag Information field(s) are omitted.) |
==============================================================================
An access bit value of one indicates access to the element by a medium
transport element is allowed. An access bit of zero indicates access to the
element by the medium transport element is denied.
The source storage element address field provides the address of the last
storage element this unit of media was moved from. This element address value
may or may not be the same as this element. This field is valid only if the
SValid bit is one.
For fields not defined in this section, see 16.2.5.3.
16.2.5.5. Import Export Element Descriptor
Table 16-13: Import Export Element Descriptor
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | (MSB) |
-----|--- Element Address ---|
1 | (LSB) |
-----|-----------------------------------------------------------------------|
2 | Reserved | InEnab | ExEnab | Access | Except | ImpExp | Full |
-----|-----------------------------------------------------------------------|
3 | Reserved |
-----|-----------------------------------------------------------------------|
4 | Additional Sense Code |
-----|-----------------------------------------------------------------------|
5 | Additional Sense Code Qualifier |
-----|-----------------------------------------------------------------------|
6 | |
-----|- - - Reserved - - -|
8 | |
-----|-----------------------------------------------------------------------|
9 | SValid | Invert | Reserved |
-----|-----------------------------------------------------------------------|
10 | (MSB) |
-----|--- Source Storage Element Address ---|
11 | (LSB) |
-----|-----------------------------------------------------------------------|
12 | |
- - -|- - - Primary Volume Tag Information - - -|
47 | (Field omitted if PVolTag = 0) |
-----|-----------------------------------------------------------------------|
48 | |
- - -|- - - Alternate Volume Tag Information - - -|
83 | (Field omitted if PVolTag = 0) |
-----|-----------------------------------------------------------------------|
84 | |
- - -|- - - Reserved - - -|
87 | (Field moved up if Volume Tag Information field(s) are omitted.) |
-----|-----------------------------------------------------------------------|
88 | |
- - -|- - - Vendor Unique - - -|
z-1 | (Field moved up if Volume Tag Information field(s) are omitted.) |
==============================================================================
An import enable (InEnab) bit of one indicates that the import export
element supports movement of media into the scope of the medium changer
device. An InEnab bit of zero indicates that this element does not support
import actions.
An export enable (ExEnab) bit of one indicates that the import export
element supports movement of media out of the scope of the medium changer
device. An ExEnab bit of zero indicates that this element does not support
export actions.
An access bit of one indicates that access to the import export element by a
medium transport element is allowed. An access bit of zero indicates access
to the import export element by medium transport elements is denied.
IMPLEMENTORS NOTE: An example of when access would be denied is when the
operator has exclusive access to the import export element.
An import export (ImpExp) bit of one indicates the unit of media in the
import export element was placed there by an operator. An ImpExp bit of zero
indicates the unit of media in the import export element was placed there by
the medium transport element.
For fields not defined in this section, see 16.2.5.3.
16.2.5.6. Data Transfer Element Descriptor
Table 16-14: Data Transfer Element Descriptor
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | (MSB) |
-----|--- Element Address ---|
1 | (LSB) |
-----|-----------------------------------------------------------------------|
2 | Reserved | Access | Except |Reserved| Full |
-----|-----------------------------------------------------------------------|
3 | Reserved |
-----|-----------------------------------------------------------------------|
4 | Additional Sense Code |
-----|-----------------------------------------------------------------------|
5 | Additional Sense Code Qualifier |
-----|-----------------------------------------------------------------------|
6 |Not Bus|Reserved|ID Valid|LU Valid|Reserved| Logical Unit Number |
-----|-----------------------------------------------------------------------|
7 | SCSI Bus Address |
-----|-----------------------------------------------------------------------|
8 | Reserved |
-----|-----------------------------------------------------------------------|
9 | SValid | Invert | Reserved |
-----|-----------------------------------------------------------------------|
10 | (MSB) |
-----|--- Source Storage Element Address ---|
11 | (LSB) |
-----|-----------------------------------------------------------------------|
12 | |
- - -|- - - Primary Volume Tag Information - - -|
47 | (Field omitted if PVolTag = 0) |
-----|-----------------------------------------------------------------------|
48 | |
- - -|- - - Alternate Volume Tag Information - - -|
83 | (Field omitted if PVolTag = 0) |
-----|-----------------------------------------------------------------------|
84 | |
- - -|- - - Reserved - - -|
87 | (Field moved up if Volume Tag Information field(s) are omitted.) |
-----|-----------------------------------------------------------------------|
88 | |
- - -|- - - Vendor Unique - - -|
z-1 | (Field moved up if Volume Tag Information field(s) are omitted.) |
==============================================================================
An access bit value of one indicates access to the data transfer element by
the medium transport element is allowed. A value of zero indicates access to
the data transfer element by a medium transport element is denied.
IMPLEMENTORS NOTE: Access to the data transfer element by medium transport
elements might be denied if a data transfer operation were under way. Note
that a one value in this bit may not be sufficient to ensure a successful
operation. This bit can only reflect the best information available to the
medium changer device, which may not accurately reflect the state of the
primary (data transfer) device.
A not this bus (Not Bus) bit value of one indicates that the SCSI bus
address and logical unit number values are not valid for the SCSI bus used to
select the medium changer device. A Not Bus bit value of zero indicates that
the SCSI address and logical unit values, if valid, are on the same bus as the
medium changer device.
An ID Valid bit value of one indicates that the SCSI bus address field
contains valid information. An LU Valid bit value of one indicates that the
logical unit number field contains valid information.
The SCSI bus address field, if valid, provides the SCSI address (binary
representation) of the primary device served by the medium changer at this
element address.
The logical unit number field, if valid, provides the logical unit number
within the SCSI bus device of the primary device served by the medium changer
at this element address.
For fields not defined in this section, see 16.2.5.3.
16.2.6. REQUEST VOLUME ELEMENT ADDRESS Command
Table 16-15: REQUEST VOLUME ELEMENT ADDRESS Command
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | Operation Code (B5h) |
-----|-----------------------------------------------------------------------|
1 | Logical Unit Number | VolTag | Element Type Code |
-----|-----------------------------------------------------------------------|
2 | (MSB) |
-----|--- Element Address ---|
3 | (LSB) |
-----|-----------------------------------------------------------------------|
4 | (MSB) |
-----|--- Number of Elements ---|
5 | (LSB) |
-----|-----------------------------------------------------------------------|
6 | Reserved |
-----|-----------------------------------------------------------------------|
7 | (MSB) |
-----|--- ---|
8 | Allocation Length |
-----|--- ---|
9 | (LSB) |
-----|-----------------------------------------------------------------------|
10 | Reserved |
-----|-----------------------------------------------------------------------|
11 | Control |
==============================================================================
The REQUEST VOLUME ELEMENT ADDRESS command (Table 16-15) is used to transfer
the results of a SEND VOLUME TAG command. Multiple REQUEST VOLUME ELEMENT
ADDRESS commands may be used to recover the results of a single SEND VOLUME
TAG command with the translate option.
For each SEND VOLUME TAG command, the target shall be able to report
multiple elements that match a volume tag template in element address order.
Once information for a given element address has been reported, only higher
element addresses will be reported by subsequent REQUEST VOLUME ELEMENT
ADDRESS commands.
IMPLEMENTORS NOTE: In order to ensure the successful completion of a SEND
VOLUME TAG, REQUEST VOLUME ELEMENT ADDRESS sequence in a multi-initiator
environment it may be necessary to reserve the medium changer device. To do
this, issue a unit RESERVE command prior to the SEND VOLUME TAG command and
delay issuing the RELEASE until after the last REQUEST VOLUME ELEMENT
ADDRESS.
A volume tag (VolTag) bit of one indicates that the target shall report
volume tag information. A value of zero indicates that volume tag information
shall not be reported. This is provided for compatibility with the READ
ELEMENT STATUS command.
The element type code field specifies the particular element type(s)
selected for reporting by this command. A value of zero specifies that status
for all element types shall be reported. The codes for this field are defined
in Table 16-8. This acts as a qualification of the element(s) determined by
SEND VOLUME TAG to match the template specified.
The element address field gives a medium changer element address whose
interpretation depends on the send action code received with the last SEND
VOLUME TAG command. This code is echoed in the volume element address return
format transferred by this command. When the last send action code was a
translate, (code values 0h .. 7h), the element address field gives the minimum
element address to be reported by this command. When the send action code is
other than translate, (i.e. assert, replace, and undefined, code values
8h .. Dh), the element address field gives the particular element whose volume
tag information was modified.
The number of elements specifies the maximum number of elements and volume
tags to be reported by the target for this command. The value specified by
this field is not the range of element addresses to be considered for
reporting but rather the number of elements to report of those that match the
last send volume tag translate template. If the allocation length is not
sufficient to transfer all the element descriptors, the target shall transfer
all those descriptors that can be completely transferred and this shall not be
considered an error.
The data returned by this command consists of a header as defined by Table
16-16, plus one or more element type specific pages in the same format as
defined by the READ ELEMENT STATUS command. (See Tables 16-10 - 16-14.)
Table 16-16: Volume Element Address Header Format
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | (MSB) |
-----|--- First Element Address Reported ---|
1 | (LSB) |
-----|-----------------------------------------------------------------------|
2 | (MSB) |
-----|--- Number of Elements Reported ---|
3 | (LSB) |
-----|-----------------------------------------------------------------------|
4 | Reserved | Send Action Code |
-----|-----------------------------------------------------------------------|
5 | (MSB) |
-----|--- ---|
6 | Byte Count of Report Available |
-----|--- (all pages, x - 7 ) ---|
7 | (LSB) |
==============================================================================
8 to | |
- - -|- - - Element Status Page(s) - - -|
x | |
==============================================================================
The send action code field gives the function performed by the last SEND
VOLUME TAG command as listed in Table 16-21. This command reports the results
of this send action code operation.
For fields not defined in this section, see 16.2.5.1.
16.2.7. RELEASE Command
Table 16-17: RELEASE Command
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | Operation Code (17h) |
-----|-----------------------------------------------------------------------|
1 | Logical Unit Number | 3rdPty | Third Party Device ID | Element|
-----|-----------------------------------------------------------------------|
2 | Reservation Identification |
-----|-----------------------------------------------------------------------|
3 | Reserved |
-----|-----------------------------------------------------------------------|
4 | Reserved |
-----|-----------------------------------------------------------------------|
5 | Control |
==============================================================================
The RELEASE command (Table 16-17) is used to release previously reserved
units, or, if the element release option is implemented, previously reserved
elements within units. It is not an error for an initiator to attempt to
release a reservation that is not currently active. In this case, the target
shall return GOOD status without altering any other reservation.
16.2.7.1. Logical Unit Release.
If the element bit is zero, this command shall cause the target to terminate
all non-third party unit and element reservations that are active from the
initiator to the specified logical unit.
16.2.7.2. Element Release (Optional).
If the element bit is one and the element release option is not implemented,
the RELEASE command shall be terminated with CHECK CONDITION status and the
sense key shall be set to ILLEGAL REQUEST. This option shall be implemented
if the element reservation option (see 16.2.8.1) is implemented.
If the element bit is one and the element release option is implemented,
this command shall cause any reservation from the requesting initiator with a
matching reservation identification to be terminated. Other reservations from
the requesting initiator shall remain in effect.
16.2.7.3. Third Party Release
The third-party release option of the RELEASE command allows an initiator to
release a unit or elements within a unit that were previously reserved using
third-party reservation (see 16.2.8.3). Third-party release shall be
implemented if third-party reserve is implemented.
If the third-party (3rdPty) bit is zero, the third-party release option is
not requested. If the 3rdPty bit is one and the target implements the third-
party release option, the target shall release the specified unit or elements,
but only if the reservation was made using the third-party reservation option
by the initiator that is requesting the release for the same SCSI device as
specified in the third-party device ID field.
If the 3rdPty bit is one and the target does not implement the third-party
release option, the target shall terminate the command with CHECK CONDITION
status and the sense key shall be set to ILLEGAL REQUEST.
16.2.8. RESERVE Command
Table 16-18: RESERVE Command
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | Operation Code (16h) |
-----|-----------------------------------------------------------------------|
1 | Logical Unit Number | 3rdPty | Third Party Device ID | Element|
-----|-----------------------------------------------------------------------|
2 | Reservation Identification |
-----|-----------------------------------------------------------------------|
3 | (MSB) |
-----|--- Element List Length ---|
4 | (LSB) |
-----|-----------------------------------------------------------------------|
5 | Control |
==============================================================================
The RESERVE command (Table 16-18) is used to reserve units or, if the
element reservation option is implemented, elements within units for the use
of the initiator. The third-party reservation allows units or elements to be
reserved for another specified SCSI device. The RESERVE and RELEASE commands
provide the basic mechanism for contention resolution in multiple-initiator
systems.
16.2.8.1. Logical Unit Reservation
If the element bit is zero, this command shall request that the entire unit
be reserved for the exclusive use of the initiator until the reservation is
superseded by another valid RESERVE command from the initiator that made the
reservation or until released by a RELEASE command from the same initiator
that made the reservation, by a BUS DEVICE RESET message from any initiator,
by a hard RESET condition, or by a power off/on cycle. A unit reservation
shall not be granted if the unit or any element is reserved by another
initiator. It shall be permissible for an initiator to reserve a unit that is
currently reserved by that initiator. If the element bit is zero, the
reservation identification and the element list length shall be ignored.
If the unit, or any element within the unit is reserved for another
initiator, the target shall respond by returning RESERVATION CONFLICT status.
If, after honoring the reservation, any other initiator attempts to perform
any command on the reserved unit other than an INQUIRY, REQUEST SENSE, ALLOW
MEDIUM REMOVAL, RESERVE, or a RELEASE command, the command shall be rejected
with RESERVATION CONFLICT status.
16.2.8.2. Element Reservation (Optional)
The reservation identification provides a means for an initiator to identify
each element reservation. This allows an initiator in a multiple-tasking
environment, to have multiple reservations outstanding. The reservation
identification is used in the RELEASE command to specify which reservation is
to be released. It is also used in superseding RESERVE commands to specify
which reservation is to be superseded.
If the element reservation option is implemented, the element release option
(see 16.2.7.2) shall also be implemented. These options permit multiple
elements within the unit to be reserved, each with a separate reservation
identification.
If the element bit is one, and the element reservation option is
implemented, the target shall process the reservation request as follows:
(1) The element list shall be checked for valid element addresses. If any
element address is invalid for this unit, the command shall be terminated with
CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST. The
element list shall be checked for invalid element overlaps with other element
descriptors in the element list and if invalid overlaps are found, the command
shall be terminated with CHECK CONDITION status and the sense key shall be set
to ILLEGAL REQUEST.
(2) If the requested reservation does not conflict with any active or
previously requested reservation, the elements specified shall be reserved
until superseded by another valid RESERVE command from the initiator that made
the reservation or until released by a RELEASE command from the same
initiator, by a BUS DEVICE RESET message from any initiator, or by a hard
RESET condition. If either of the last two conditions occur, the next command
from each initiator shall be terminated with CHECK CONDITION status and the
sense key shall be set to UNIT ATTENTION.
(3) If the reservation request conflicts with a reservation already active
the target shall return RESERVATION CONFLICT status.
If the element bit is one, and the element reservation option is not
implemented, the RESERVE command shall be terminated with CHECK CONDITION
status. The sense key shall be set to ILLEGAL REQUEST.
Table 16-19: Data Format of Element List Descriptors
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | |
- - -|- - - Reserved - - -|
1 | |
-----|-----------------------------------------------------------------------|
2 | (MSB) |
-----|--- Number of Elements ---|
3 | (LSB) |
-----|-----------------------------------------------------------------------|
4 | (MSB) |
-----|--- Element Address ---|
5 | (LSB) |
==============================================================================
The size of the element list shall be defined by the element list length
parameter. The element list shall consist of zero or more descriptors as
shown in Table 16-19. Each element list descriptor defines a series of
elements beginning at the specified element address for the specified number
of elements. If the number of elements is zero, the element list shall begin
at the specified element address and continue through the last element address
on the unit.
If an initiator issues a command to an element that has been reserved by a
different initiator, the command shall not be performed and the command shall
be terminated with a RESERVATION CONFLICT status. If a reservation conflict
precludes any part of the command, none of the command shall be performed.
16.2.8.3. Third Party Reservation
The third-party reservation option of the RESERVE command allows an
initiator to reserve a unit or elements within a unit for another SCSI device.
If the third-party (3rdPty) bit is zero, the third-party reservation option
is not requested. If the 3rdPty bit is one and the third-party reservation
option is implemented, the RESERVE command shall reserve the specified unit or
elements for the SCSI device specified in the third-party device ID field.
The target shall preserve the reservation until it is superseded by another
valid RESERVE command from the initiator that made the reservation or until it
is released by the same initiator, by a BUS DEVICE RESET message from any
initiator, or a hard RESET condition. The target shall ignore any attempt to
release the reservation made by any other initiator.
If the 3rdPty bit is one and the third-party reservation option is not
implemented, the target shall reject the RESERVE command with CHECK CONDITION
status and the sense key shall be set to ILLEGAL REQUEST.
16.2.8.4. Superseding Reservations
An initiator that holds a current reservation may modify that reservation by
issuing another RESERVE command to the same unit and, if the element bit is
one, using the same reservation identification. The superseding RESERVE
command shall release the previous reservation in place when the new
reservation request is granted. The current reservation shall not be modified
if the new reservation request cannot be granted. If the superseding
reservation cannot be granted because of conflicts with a previous active
reservation (other than the reservation being superseded), the target shall
return RESERVATION CONFLICT status.
IMPLEMENTORS NOTE: Superseding reservations are principally intended to
allow the SCSI device ID to be changed on a reservation using the third-
party reservation option.
16.2.9. SEND VOLUME TAG Command
Table 16-20: SEND VOLUME TAG Command
=============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | Operation Code (B6h) |
-----|-----------------------------------------------------------------------|
1 | Logical Unit Number |Reserved| Element Type Code |
-----|-----------------------------------------------------------------------|
2 | (MSB) |
-----|--- Element Address ---|
3 | (LSB) |
-----|-----------------------------------------------------------------------|
4 | Reserved |
-----|-----------------------------------------------------------------------|
5 | Reserved | Send Action Code |
-----|-----------------------------------------------------------------------|
6 | |
-----|--- Reserved ---|
7 | |
-----|-----------------------------------------------------------------------|
8 | (MSB) |
-----|--- Parameter List Length ---|
9 | (LSB) |
-----|-----------------------------------------------------------------------|
10 | Reserved |
-----|-----------------------------------------------------------------------|
11 | Control |
==============================================================================
The SEND VOLUME TAG command (Table 16-20) transfers a volume tag template to
be searched for or new volume tag information for one or more media changer
elements. The function of the command is conveyed by the Send Action Code
field. The REQUEST VOLUME ELEMENT ADDRESS command is used to transfer the
results of a translate search operation.
The element type code field specifies an element type specification as
defined by Table 16-8. If the send action code indicates a translate
operation this field indicates the element types to be searched. If this is a
zero, all element types are candidates for a translate operation. If the Send
action code does not indicate a translate, this field shall be treated as
reserved.
The send action code field gives the function to be performed by this
command as listed in Table 16-21.
Table 16-21: Send Volume Tag Action Codes
==============================================================================
Code Description
----- ----------------------------------------------------------------
0h Translate - search all defined volume tags.
1h Translate - search only primary volume tags.
2h Translate - search only alternate volume tags.
3h Reserved
4h Translate - search all defined tags - ignore sequence numbers.
5h Translate - search primary tags - ignore sequence numbers.
6h Translate - search alternate tags - ignore sequence numbers.
7h Reserved
8h Assert - as the primary volume tag - if tag now undefined.
9h Assert - as the alternate volume tag - if tag now undefined.
Ah Replace - the primary volume tag - current tag ignored.
Bh Replace - the alternate volume tag - current tag ignored.
Ch Undefined - the primary volume tag - current tag ignored.
Dh Undefined - the alternate volume tag - current tag ignored.
Eh-1Bh Reserved
1Ch-1Fh Vendor Specific
==============================================================================
Translate operations request that the target search the volume tag
information available to it for elements whose volume tag information matches
the template given by the command parameters. The resulting information is
reported via the REQUEST VOLUME ELEMENT ADDRESS command.
Assert operations define volume tag information for a single element. A
CHECK CONDITION with ILLEGAL REQUEST is reported if the subject element
already has defined volume tag information, in this case the original volume
tag information shall remain unaltered.
Replace operations define volume tag information for a single element. Any
previously defined volume tag information is overwritten.
Undefined operations cause previously defined volume tag information for the
specified element to be cleared. It shall not be considered an error to
undefined volume tag information that was not previously defined.
A medium changer device that implements volume tag information may choose to
not implement the facilities that modify the volume tag information. With
such an implementation a request for the assert, replace or undefined
functions would cause the SEND VOLUME TAG command to be terminated with CHECK
CONDITION and a sense key of ILLEGAL REQUEST.
The element address field gives a medium changer element address whose
interpretation depends on the send action code received with this command.
When the send action code is a translate, (code values 0h .. 7h), the Element
Address field gives the starting element to be examined for satisfaction of
the search criteria. When the send action code is other than translate, (i.e.
assert, replace, and undefined, code values 8h .. Dh), the element address
field gives the particular element whose volume tag information is to be
modified.
The volume tag information used for translate, assert and replace functions
is defined in Table 16-22. No parameters are necessary for undefined
operations.
Table 16-22: Send Volume Tag Parameters Format
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | |
- - -|- - - Volume Identification Template Field - - -|
31 | |
-----|-----------------------------------------------------------------------|
32 | |
-----|--- Reserved ---|
33 | |
-----|-----------------------------------------------------------------------|
34 | (MSB) |
- - -|--- Minimum Volume Sequence Number ---|
35 | (LSB) |
-----|-----------------------------------------------------------------------|
36 | |
-----|- - - Reserved - - -|
37 | |
-----|-----------------------------------------------------------------------|
38 | (MSB) |
- - -|--- Maximum Volume Sequence Number ---|
39 | (LSB) |
==============================================================================
The volume identification template field specifies a search template for
translate functions and the exact value of the new volume identification
information for other SEND VOLUME TAG command functions.
As a search template, this field may contain the wildcard characters '*' and
'?' (2Ah and 3Fh). '*' will match any string of characters, when it appears in
a template the remainder of the template is not used. '?' will match any
single character.
For a function other than translate, this field may not contain the '*' or
'?' wildcard characters.
The minimum volume sequence number field specifies the new sequence number
for the assert and replace functions. For a translate, this specifies the
least value that will meet the search specification.
The maximum volume sequence number field specifies the greatest value that
will meet the search specification. This field is ignored on functions other
than translate.
16.3. Parameters for Medium Changer Devices
16.3.1. Diagnostic Parameters
This section defines the descriptors and pages for diagnostic parameters
used with medium changer devices.
The diagnostic page codes for medium changer devices are defined in Table
16-23.
Table 16-23: Diagnostic Page Codes
==============================================================================
Page Code Description Section
------------------------------------------------------------------------------
00h Supported Diagnostic Pages 7.3.1.1
01h - 3Fh Reserved (for all device type pages)
40h - 7Fh Reserved
80h - FFh Vendor-specific pages
==============================================================================
16.3.2. Log Parameters
This section defines the descriptors and pages for log parameters used with
medium changer devices.
The log page codes for medium changer devices are defined in Table 16-24.
Table 16-24: Log Page Codes
==============================================================================
Page Code Description Section
------------------------------------------------------------------------------
00h Supported Log Pages 7.3.2.5
06h Non-Medium Error Page 7.3.2.4
07h Last n Error Events Page 7.3.2.3
01h - 05h, 08h - 2Fh, 3Fh Reserved
30h - 3Eh Vendor-specific pages
==============================================================================
16.3.3. Mode Parameters
This section defines the descriptors and pages for mode parameters used with
medium changer devices.
The mode parameter list, including the mode parameter header and mode block
descriptor are defined in 7.3.3.
The medium-type code field is contained in the mode parameter header (see
Table 7-61 and 7-62). This field is reserved for medium changer devices.
The device specific parameter field is contained in the mode parameter
header (see Table 7-61 and 7-62). This field is reserved for medium changer
devices.
The density code field is contained in the mode parameter block descriptor
(see Table 7-63). This field is reserved for medium changer devices.
The mode page codes for medium changer devices are shown in Table 16-25.
Table 16-25: Mode Page Codes
==============================================================================
Page Code Description Section
------------------------------------------------------------------------------
1Fh Device Capabilities 16.3.3.1
1Dh Element Address Assignment 16.3.3.2
1Eh Transport Geometry Parameters 16.3.3.3
01h - 1Dh Reserved
00h Vendor Specific (does not require page format)
20h - 3Eh Vendor-specific Pages
3Fh Returns all pages (valid only for the MODE SENSE command)
==============================================================================
16.3.3.1. Device Capabilities Page
Table 16-26: Device Capabilities Page
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | PS |Reserved| Page Code (1Fh) |
-----|-----------------------------------------------------------------------|
1 | Parameter Length (12h) |
-----|-----------------------------------------------------------------------|
2 | Reserved | StorDT | StorI/E| StorST | StorMT |
-----|-----------------------------------------------------------------------|
3 | Reserved |
-----|-----------------------------------------------------------------------|
4 | Reserved | MT->DT | MT->I/E| MT->ST | MT->MT |
-----|-----------------------------------------------------------------------|
5 | Reserved | ST->DT | ST->I/E| ST->ST | ST->MT |
-----|-----------------------------------------------------------------------|
6 | Reserved |I/E->DT |I/E->I/E|I/E->ST |I/E->MT |
-----|-----------------------------------------------------------------------|
7 | Reserved | DT->DT | DT->I/E| DT->ST | DT->MT |
-----|-----------------------------------------------------------------------|
8 to | |
- - -|- - - Reserved - - -|
11 | |
-----|-----------------------------------------------------------------------|
12 | Reserved | MT<>DT | MT<>I/E| MT<>ST | MT<>MT |
-----|-----------------------------------------------------------------------|
13 | Reserved | ST<>DT | ST<>I/E| ST<>ST | ST<>MT |
-----|-----------------------------------------------------------------------|
14 | Reserved |I/E<>DT |I/E<>I/E|I/E<>ST |I/E<>MT |
-----|-----------------------------------------------------------------------|
15 | Reserved | DT<>DT | DT<>I/E| DT<>ST | DT<>MT |
==============================================================================
The parameters savable (PS) bit is only used with the MODE SENSE command.
This bit is reserved with the MODE SELECT command. A PS bit of one indicates
that the target is capable of saving the page in a non-volatile vendor-
specific location.
The device capabilities page (Table 16-26) defines characteristics of the
element types on this medium changer implementation. This information may be
employed by the initiator to determine functions permitted by the MOVE MEDIUM
and EXCHANGE MEDIUM commands.
In the field names on this page, the following element type abbreviations
are used:
MT a medium transport element,
ST a storage element,
I/E an import export element, and
DT a data transfer element.
In the descriptions, XX and YY are any of the element type abbreviations.
A StorXX bit value of one indicated that the defined elements of type XX may
provide independent storage for a unit of media. A value of zero indicates
that elements of type XX provide virtual sources or destinations, that the
location of the unit of media is provided by an element of some other type.
The value of StorST is one by the definition of that type. See 16.1.1.
An XX->YY bit value of one indicates that the medium changer device supports
MOVE MEDIUM commands where the source is element type XX and the destination
is element type YY. An XX->YY bit value of zero indicates that these MOVE
MEDIUM commands will be rejected with ILLEGAL REQUEST.
An XX<>YY bit value of one indicates that the medium changer device supports
EXCHANGE MEDIUM commands where the source is element type XX, destination 1 is
element type YY, and destination 2 is the same type as the source element
type. These bits indicate the support for the possible types of simple
exchange operations. An XX<>YY bit value of zero indicates that these
EXCHANGE MEDIUM commands will be rejected with ILLEGAL REQUEST.
16.3.3.2. Element Address Assignment Page
Table 16-27: Element Address Assignment Page
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | PS |Reserved| Page Code (1Dh) |
-----|-----------------------------------------------------------------------|
1 | Parameter Length (12h) |
-----|-----------------------------------------------------------------------|
2 | (MSB) |
-----|--- Medium Transport Element Address ---|
3 | (LSB) |
-----|-----------------------------------------------------------------------|
4 | (MSB) |
-----|--- Number of Medium Transport Elements ---|
5 | (LSB) |
-----|-----------------------------------------------------------------------|
6 | (MSB) |
-----|--- First Storage Element Address ---|
7 | (LSB) |
-----|-----------------------------------------------------------------------|
8 | (MSB) |
-----+--- Number of Storage Elements ---|
9 | (LSB) |
-----|-----------------------------------------------------------------------|
10 | (MSB) |
-----|--- First Import Export Element Address ---|
11 | (LSB) |
-----|-----------------------------------------------------------------------|
12 | (MSB) |
-----|--- Number of Import Export Elements ---|
13 | (LSB) |
-----|-----------------------------------------------------------------------|
14 | (MSB) |
-----|--- First Data Transfer Element Address ---|
15 | (LSB) |
-----|-----------------------------------------------------------------------|
16 | (MSB) |
-----|--- Number of Data Transfer Elements ---|
17 | (LSB) |
-----|-----------------------------------------------------------------------|
18 | |
-----|--- Reserved ---|
19 | |
==============================================================================
The parameters savable (PS) bit is only used with the MODE SENSE command.
This bit is reserved with the MODE SELECT command. A PS bit of one indicates
that the target is capable of saving the page in a non-volatile vendor-
specific location.
The element address assignment page (Table 16-27) is used to assign
addresses to the elements of the medium changer (MODE SELECT) and to report
those assignments (MODE SENSE). This page also defines the number of each type
of element present.
The first medium transport element address field identifies the first medium
transport element contained in the medium changer (other than the default
medium transport address of zero). The number of medium transport elements
field defines the total number of medium transport elements contained in the
medium changer. If the number of medium transport elements field in a MODE
SELECT command is greater than the default value returned in the MODE SENSE
parameter data, the target shall return CHECK CONDITION status and set the
sense key to ILLEGAL REQUEST.
The first storage element address field identifies the first medium storage
element contained in the medium changer. The number of storage elements field
defines the total number of medium storage elements contained in the medium
changer. If the number of medium storage elements field in a MODE SELECT
command is greater than the default value returned in the MODE SENSE parameter
data, the target shall return CHECK CONDITION status and set the sense key to
ILLEGAL REQUEST.
The first import export element address field identifies the first medium
portal that is accessible both by the medium transport devices and also by an
operator from outside the medium changer. The number of import export elements
field defines the total number of import export elements contained in the
medium changer and accessible to the medium transport elements. If the number
of import export elements field in a MODE SELECT command is greater than the
default value returned in the MODE SENSE parameter data, the target shall
return CHECK CONDITION status and set the sense key to ILLEGAL REQUEST .
IMPLEMENTORS NOTE: The number of import export elements may be zero.
The first data transfer element address field identifies the first data
transfer element contained in the medium changer. The data transfer elements
may be either read/write or read-only devices. The number of data transfer
field defines the total number of data transfer elements contained within the
medium changer and accessible to the medium transport elements. If the number
of data transfer elements field in a MODE SELECT command is greater than the
default value returned in the MODE SENSE parameter data, the target shall
return CHECK CONDITION status and set the sense key to ILLEGAL REQUEST .
Each element in the medium changer must have a unique address. If the
address ranges defined for any of the element types overlap, the target shall
return CHECK CONDITION status and set the sense key to ILLEGAL REQUEST.
16.3.3.3. Transport Geometry Parameters Page
Table 16-28: Transport Geometry Parameters Page
==============================================================================
Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Byte | | | | | | | | |
==============================================================================
0 | PS |Reserved| Page Code (1Eh) |
-----|-----------------------------------------------------------------------|
1 | Parameter Length |
==============================================================================
| Transport Geometry Descriptor(s) |
==============================================================================
0 | Reserved | Rotate |
-----|-----------------------------------------------------------------------|
1 | Member Number in Transport Element Set |
==============================================================================
The parameters savable (PS) bit is only used with the MODE SENSE command.
This bit is reserved with the MODE SELECT command. A PS bit of one indicates
that the target is capable of saving the page in a non-volatile vendor-
specific location.
The transport geometry parameters page (Table 16-28) defines whether each
medium transport element is a member of a set of elements that share a common
robotics subsystem and whether the element is capable of media rotation. One
transport geometry descriptor is transferred for each medium transport
element, beginning with the first medium transport element. (Other than the
default transport element address of zero.)
The parameter length specifies the number of bytes of transport geometry
descriptors that follow. The geometry of each medium transport element is
defined using a two-byte field as defined below.
A rotate bit of one indicates that the medium transport element supports
media rotation for handling double-sided media. A rotate bit of zero
indicates that the medium transport element does not support media rotation.
The member number in set indicates the position of this element in a set of
medium transport elements that share a common robotics subsystem. The first
element in a set has a member number of zero.
16.4. Glossary for Medium Changer Devices
data transfer element. A component of a medium changer used to access the data
stored on a unit of media. The address in medium changer element space of a
primary device.
element. An addressable physical component of a medium changer device that can
serve as the location of a unit of media.
import export element. A location within a medium changer device that can be
accessed by both the medium transport elements and by the operator.
medium transport element. A component of a medium changer device that is used
to move units of media.
media rotation. The process of changing the orientation of a unit of media. In
particular this refers to inverting a two sided media cartridge so that a data
transport element which can access only side at a time can access data on the
other side.
primary device. A device for reading or writing data on medium. These devices
would typically implement the direct access, sequential access, optical memory
device or CD-ROM command sets in this standard. Examples are magnetic disk
drives, cartridge tape drives, optical disk drives and CD-ROM drives. Use in
a medium changer environment implies that the device supports removable media.
storage element. A component of a medium changer device used for inactive
storage of a unit of media.
(This page is intentionally blank.)
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