Error Logs - HP 7936 Support Manual

Troubleshooting and Diagnostics
7936 and 7937
In addition to retrieving drive status, the exerciser
also provides access to the various fault and error
logs maintained by the drive. This log information
can be invaluable in isolating drive problems.
8-11. ERROR LOGS
In addition to the LED display and the drive
status, the drive also maintains several internal logs
to record error information. The contents of these
logs can be accessed using the appropriate external
exerciser command. Details of these logs are
provided in the following paragraphs.
8-12.
ERROR RATE TEST (ERT) LOG
This log contains read data errors detected during
an Error Rate Test (ERT). Data errors are initially
logged in controller RAM, which holds a maxi-
mum of 5 entries. Periodically, the drive transfers
the log entries from RAM to the ERT log on the
disc maintenance tracks. There is a separate ERT
log for each data head. The ERT log is located on
the 00 maintenance track and can hold a maxi-
mum of
101
log entries. The drive returns both
RAM and disc entries when the fault log is read;
therefore, a total of
106
ERT log entries can be
returned for each head.
The log header includes the following information:
• Total number of data error entries
• Number of sectors transferred (by cor-
responding head)
• Number of correctable (by ECC) data errors
• Number of uncorrectable (by ECC) data
errors
After the header information, there is an entry for
each unique sector address that experienced one or
more errors during the ERT. If there were multiple
errors on the same sector, the information in the
Error Code Byte represents all the errors that oc-
curred. The counters in the log header are incre-
mented for each error.
Each data error entry includes the following
8-4
information:
• Logical address (cylinder, head, and sector) of
the error
• Error Code Byte. This byte is defined in
figure
8-1.
• Error type
• Occurrence count
8-13. RUN TIME LOG
The run time log contains data errors detected
during operation of the drive, excluding those that
occur during an ERT. The structure of the run
time log is identical to that of the ERT log.
However, there are important differences in the
significance of some of the data fields. These dif-
ferences are summarized below:
• The "number of correctable data errors" field
in the run time log header indicates the num-
ber of times a single retry was required to
recover data in a sector. Data errors corree-
tntl solely by ECC (no retry required) are ig-
nored. Although counted, correctable errors
are
not
entered in the run time log.
• The "number of uncorrectable data errors"
field in the run time log header indicates the
number of times two or more retries were
required to recover data. Whether or not the
data was ultimately recovered is indicated by
the Error Code Byte for the sector. The drive
uses a default retry time of
800
milliseconds,
which equates to roughly
40
read attempts
before the data is declared unrecoverable.
All uncorrectable data errors are entered in
the run time log.
• The run time log data error entries include
only
IIncorrectahle
errors. The significance of
the Error Code Byte returned with each run
time log entry is shown in figure 8-2.