DVCID:
If the DVCID bit is set the media changer will return device identifiers for the Data Transfer
element. A DVCID bit of zero specifies that the device shall not return device identifiers.
Allocation Length:
This field specifies the number of bytes that the initiator has allocated for returned data. Note that
the Read Element Status command can be issued with an Allocation Length specified as 8 bytes
(the length of the status page header) to determine the Allocation Length required to transfer all of
the element status data that become available as a result of the command.
Element Status Data
Data returned by the Read Element Status command is described below. The Element Status Data
consists of an 8-byte Header followed by one or more status pages (for each element type). The status
pages are made up of an 8-byte sub-header and one or more element descriptors (one for each element
address).
Header
The data returned on a Read Element Status command always starts with the Header. This Header
reports the first element address, the number of elements, and the byte count of the report.
Bit 7 6 5 4 3 2 1 0
Byte
0 - 1 First Element Address Reported
2 - 3 Number of Elements Available
4 Reserved
5 - 7 Byte Count of Report Available
Field descriptions:
First Element Address Reported:
This field indicates the element address of the element with the smallest element address found to
meet the Read Element Status command's request.
Number of Elements Available:
This field indicates the number of elements found. The status for these elements is returned if the
Allocation Length specified in the Read Element Status command's CDB was sufficient.
Byte Count of Report Available:
This field indicates the number of available element status bytes that meet the CDB requirements.
This value does not adjust to match the Allocation Length field of the CDB and does not include
the 8 byte element status header.
Element Status Page (Sub-header and Element Descriptor)
The Element Status Page includes an 8-byte sub-header and one or more element descriptors. The
sub-header includes the element type code, the settings for PVolTag and AVolTag, the length of each
descriptor block, and the number of bytes of descriptor information that follow the header for the element.
Bit 7 6 5 4 3 2 1 0
Byte
0 Element Type Code
1 PvolTag AvolTag Reserved
2 - 3 Element Descriptor Length
3-54 TL2000 and TL4000 SCSI Reference
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