Fujitsu MAN3735 Manuale Utente

C141-E124-01EN

6 - 9

If errors on the disk media which cannot be recovered from are detected, or if a recoverable error
occurs repeatedly in the same data block, it is necessary for the INIT to allocate an alternate block
for the data block where the error occurred using the REASSIGN BLOCKS command.  The
procedure for alternate block processing is shown below.

An attempt will be made to copy the contents of the data area of the logical data block
specified in the "Defect Data" list to the alternate block allocated by this command, but in
some cases, the data cannot be copied.  Confirmation of the contents of data in the allocated
alternate block, saving of data before issuing this command and restoring of data after
executing this command are the responsibility of the INIT.

1) Verify data blocks in accordance with the procedure in Section 6.3 for data blocks where error

occur.  When such a data block is judged to be normal, alternate block allocation need not be
implemented.  In this case, rewrite the original data to that data block if necessary.  When the
data block is judged to be defective, implement the processing in item 2) and after.

2) Specify a logical block address for a data block which is judged to be defective and issue the

REASSIGN BLOCKS command.

3) If the REASSIGN BLOCKS command is terminated normally, verify that logical data block

according to the procedure in Section 6.3.  If that data block is judged to be correct, allocate an
alternate block and terminate processing.  When the data block is judged to be defective, return
to 2) and issue the REASSIGN BLOCKS command again, then try reallocating another
alternate block for that logical data block.

The alternate block allocation history (defect position information) is registered as an addition to
the defect list (G List).  Therefore, when reinitializing the hard disk with the FORMAT UNIT
command (see Section 6.2.2), if use of the G List is specified, defect processing can be performed
which reflects the operation results up to that time.  Also, since "Alternate sector processing" is
applied in alternate block allocation in the REASSIGN BLOCKS command, the physical
connectivity of the logical data block positions on the disk media is destroyed, but by reinitializing
the disk, as long as the number of defective sectors in the cylinder does not exceed the number of
spare sectors per cylinder, the logical data blocks are relocated by sector slip processing so that
their physical connectivity is maintained.