Reassign Blocks - HP C2488A Technical Reference Manual

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