User's Guide

Commands: Log Select (4Ch) Page 53
• Correct determination of the pages the drive uses.
• Determination of the parameter codes and length of each parameter.
The drive does not maintain a separate set of log parameters for each initiator.
Therefore, a LOG SELECT command affects all initiators.
Note: The subsequent section discusses the LOG SENSE command. The
log page codes and the log parameter codes are described in that section.
Parameter data is made up of one or more page descriptors. A page descriptor is
made up of a four-byte page header and one or more log parameters. A log
parameter is made up of a four-byte parameter header and one or more associated
parameter data bytes.
The parameter header contains a two-byte parameter code to identify the
parameter, a Parameter Control byte, and a parameter length byte.
When a counter reaches its maximum value, a log exception Check Condition is
generated if the RLEC bit is set in the Mode Select Control Mode page. The sense
data is set to Recovered Error key (01), Log Counter at Maximum qualifier, 5B/02.
Bytes 15 - 17 of the Request Sense data specify the page, MSB and LSB of the
Parameter Code respectively, which caused the Log Exception. The counters are
defined in a following section.
The drive uses pages 0, 2, 3, 30, and 31. However, the LOG SELECT command
can only select pages 2 and 3. The following table lists the LOG SELECT page
codes.
Page Page Information
Bits
5 4 3 2 1 0
2 Write error counts 0 0 0 0 1 0
3 Read error counts 0 0 0 0 1 1
Pages 30 and 31 are vendor unique and refer to the DDS Tape Log and Tape
Capacity, respectively. Page 0, the list of supported pages, is available only to the
LOG SENSE command.
Although the counts in page 30 are similar to those in pages 2 and 3, the page 2
and 3 counts are incremented separately from those in page 30. The accumulated
counts in pages 2 and 3 accumulate across cassettes after the counts are initialized
by the LOG SELECT command or since the last reset or power cycle. Thus, the
counts in those two pages can be used to accumulate events in a different way than
the counts in the log sense page 30.
If multiple log pages are sent, they must be sent in ascending order. All log
parameters of a particular page must be sent to the drive in ascending order. Not all
parameter codes need to be sent with the parameter data during the Data Out
phase. In that way, selected parameters of a particular page can be initialized to any
value desired.
The following conditions constitute errors that cause the drive to return a Check
Condition and to set sense data to Illegal Request, Invalid Parameter Data.