HP 3562A Operating Manual page 285

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USING THE DISC SERVICE FUNCTIONS
Sparing Blocks
You can use the run time and ERT logs to locate bad blocks on media. Once located, these
blocks can be spared using SPARE BLOCK. This allows you to continue using the media while
avoiding bad areas. There are four steps to sparing blocks:
For tapes, every block in the u ncorrectable and unlocatable columns in the ERT log is con­
firmed bad and needs to be spared.
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1 . View the run time log (press DISC, DISC FCTN, SERVCE FeTNS, OUTPUT LOG
then RUN TM LOG). If there are no errors in this log, there are probably no data
access problems. If there are errors recorded in this log, proceed with step 2.
2. Run the error rate test (press DISC, DISC FCTN, SERVCE FCTNS then RO ERT
TEST). NOTE: pressing RO ERT TEST erases the ERT log-view the ERT log first
to avoid erasing valuable test data. The ERT first checks all sectors by reading
their data and checking for errors. Any bad sectors are noted in the log. For discs,
the ERT then reads the log to check each bad sector individually. Each bad sector
is checked twenty times to see if errors occur consistently. The ERT then reads the
run time log to check those bad sectors twenty times also. When the ERT is
finished, proceed to step 3.
3. Any disc sector that produced a repeatable error is probably bad. View the run
time and ERT logs to see if any address appears more than once. Those that do
should be spared; proceed to step 4. Errors that occur only once are probably
random and could not be remedied by block sparing. A large number of bad
sectors could indicate other trouble.
4. To spare a block, press SPARE BLOCK then enter the block's address. This will
either be the 1-vector address or the 3-vector cylinder,head,sector address; use
the address shown in log. In 3-vector addresses, enter all three vectors at once,
separated by commas.
5. To verify sparing, you can run the ERT again. In any case, you should clear all
three logs after sparing all bad blocks and see if any errors accumulate when
you put the disc or tape back into operation.