Chapter 10. Read Element Status—B8h
38
The library does not have an import/export element. The formats of the other three
types of Element Descriptors are covered in the following tables. The first table
describes some terms that are common to all Element Descriptors.
Table 10-6: Fields Common to All Element Descriptors
Field Name
Field Length
Meaning
Element
Address
2 bytes
The address used to identify the particular element, i.e., tape picker, cartridge
storage slots, or tape drive. Each element in the library must have a unique address.
Element addresses are used by almost all medium changer device type-specific SCSI
commands to identify locations applicable to the particular command. Each element
has a factory-set default address, but the addresses can be reassigned with the
MODE
SELECT
command. The default values are listed below with the Descriptor for their
appropriate element type.
Except
1 bit
An Except bit value of 1 indicates that the element is in some sort of abnormal state.
More information on the nature of the exception is available in the Additional Sense
Code and Additional Sense Code Qualifier fields, described below.
Full
1 bit
A value of 1 indicates that the specified element contains media. A value of 0
indicates that the element does not contain media.
Additional
Sense Code
(ASC)
1 byte
The ASC and ASCQ together may provide more information about the condition
which caused the Except bit to be set to 1. Their meaning here is the same as the ASC
and ASCQ returned to the
REQUEST SENSE
command. For a listing of the meanings of all
ASC-ASCQ combinations, see
Chapter 16. SCSI Error Reporting
.
Additional
Sense Code
Qualifier (ASCQ)
1 byte
SValid
(Source Valid)
1 bit
This bit is always 0 for the library. It indicates whether the value found in the Source
Storage Element Address field is valid, a feature not implemented in the library.
Invert
1 bit
This bit is always 0 because the library does not invert cartridges.
Source Storage
Element
Address
2 bytes
This field is not used by the library because it does not track a cartridge’s previous
storage address.
Primary
Volume Tag
Information
36 bytes
If the PVolTag bit in the data header is 1, this field contains the bar code (volume tag)
information for the cartridge occupying this element. The library uses only the first
6-8 bytes of this field. If the PVolTag bit is 0, this field is omitted entirely.
