Quantum DLT 8000 Product Manual page 196

SCSI Commands
LOG SENSE Command (4Dh) (continued)
Table 5–21 Log Parameters for READ / WRITE Error LOG SENSE Page Field
Field Name
NOTE: Byte 2 of the Log Parameter Block is referred to as the Parameter Control Byte; it is made up of
six control bits plus one bit that is reserved.
DU
DS
TSD
ETC
TMC
5-52
Descriptions (continued)
Description
Disable Update. This field with a value 0 indicates that the target will
update all log parameter values. This field set to 1 indicates that the
target will not update the log parameter values except in response to
LOG SELECT. This bit is set by the drive when accumulated values reach
maximum. This is also returned set to 1 if the host set the bit in the last
LOG SELECT command. Default is 0.
Note that for parameter types other than threshold and cumulative
values, this bit is always 0.
Disable Save. Not supported; always set to 1.
Target Save Disable. Not supported; always set to 1.
Enable Threshold Comparison. When set to 1, indicates that comparison
to threshold is performed. ETC of 0 indicates that the comparison is not
performed. This bit is set to 1 by the Control Mode Page of MODE
SELECT. Default is 0.
Threshold Met Criteria. This field is valid only if host sets ETC to 1. It
determines the basis for comparison and is specified by host using LOG
SELECT. If the result of comparison is true (cumulative = threshold), and
MODE SELECT / SENSE Control Mode Page RLEC bit is set to 1, then a
UNIT ATTENTION is granted for all initiators. The sense key is set to UNIT
ATTENTION, the additional sense code to LOG EXCEPTION, and ASCQ is
set to THRESHOLD CONDITION MET. If the RLEC bit in Control Mode Page
is 0, then UNIT ATTENTION is not generated.
Note that comparison is performed in real time. A Log Sense command
need not be issued to get the check condition. Once ETC is selected, RLEC
bit in Control Mode Page, the check condition is issued based on the
criteria defined in the TMC bits if the criteria is met in real time. Check
condition will not identify for which parameter code the criteria is met.
Log Sense must be issued to read the counters to determine for which
parameter code criteria has been met.
The criteria for comparison are:
Code Basis of Comparison
00b Every update of the cumulative value
01b Cumulative value equal to threshold value
10b Cumulative value not equal to threshold value
11b Cumulative value greater than threshold value
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