Reassign Blocks
Reassign
Blocks
The
REASSIGN BLOCKS command requests
the
Target to reassign
the
defective logical
blocks
to
an
area
on
the
logical
unit
reserved for this purpose
and
to
record
the
defective
logical blocks
to
the
Grown Defect list (Glist). More
than
one physical
or
logical block
may
be relocated by each defect descriptor sent by
the
Initiator. This
command
does
not
alter
the
contents
or
location
of
the
Primary
Defect List (Plist).
Reassign Blocks Command Descriptor Block COB)
Bit
Byte
7
I
6
I
5
I
4
I
3
I
2
I
1
I
0
00
Opcode
=
om
01
Logical
Unit
Number
I
Reserved
02-04
(MSB=02)
Reserved
(LSB=04)
05
Control
Byte
The
Initiator
transfers a defect list
that
contains
the
logical block addresses
to
be
reassigned.
The
Target reassigns
the
physical media used for each logical block address in
the
list.
The
data
contained
in
the
logical blocks specified in
the
defect list will be lost,
but
the
data
in all
other
logical blocks on
the
media shall be preserved.
A specific logical block address may be reassigned more
than
once;
thus,
over
the
life
the
media, a logical block can
be
assigned to multiple physical addresses (until no more
spare
locations remain on
the
media).
Note
The
REASSIGN BLOCKS command is intended
to
be
used
to
reassign a
single block defect.
The
provision
to
handle multiple defects
in
a single
command is
made
to
allow recovery from a
situation
where multiple defects
occur on a single track. Therefore,
the
maximum length defect list
that
will
be
accepted by
the
Target is 96. Duplicate entries in
the
defect list result
in
a
single spare operation.
Reassign Blocks Defect List Header Format
Bit
Byte
7
I
6
I
5
I
4
I
3
I
2
I
1
I
0
00-01
Reserved
02-03
(MSB=02)
Defect List
Length
(LSB=03)
The
REASSIGN BLOCKS defect list contains a 4-byte header followed by one
or
more defect
descriptors.
The
length
of
each defect descriptor
is
four bytes.
Defect List Length. This field specifies
the
total
length in bytes
of
the
defect descriptors
that
follow.
The
Defect List Length is equal
to
four times
the
number
of
defect descriptors
and
does
not
include
the
Defect Header length.
DRAFT
SCSI Command Descriptions A·37
1/18/93 09:58
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