User Manual

SCSI Commands Reference Manual, Rev. J 477
www.seagate.com Parameters for direct access devices
MAXIMUM TRANSFER LENGTH field
The MAXIMUM TRANSFER LENGTH field set to a non-zero value indicates the maximum transfer length in logical blocks that the device server
accepts for a single command shown in
table 450. If a device server receives one of these commands with a transfer size greater than this value,
then the device server shall terminate the command with CHECK CONDITION status with the sense key set to ILLEGAL REQUEST and the addi-
tional sense code set to the value shown in table 451. A MAXIMUM TRANSFER LENGTH field set to 0000_0000h indicates that the device server
does not report a limit on the transfer length.
OPTIMAL TRANSFER LENGTH field
The OPTIMAL TRANSFER LENGTH field set to a non-zero value indicates the optimal transfer size in logical blocks for a single command shown
in table 450. If a device server receives one of these commands with a transfer size greater than this value, then the device server may incur sig-
nificant delays in processing the command. An OPTIMAL TRANSFER LENGTH field set to 0000_0000h indicates that the device server does not
report an optimal transfer size.
MAXIMUM PREFETCH LENGTH field
The MAXIMUM PREFETCH LENGTH field indicates the maximum prefetch length in logical blocks that the device server accepts for a single
PRE-FETCH command. The device server should set the MAXIMUM PREFETCH LENGTH field to less than or equal to the MAXIMUM TRANSFER
LENGTH field.
Table 451 Transfer limits for commands
Command
Field that specifies
the transfer size
Block Limits VPD page
field(s) that indicate
maximum limits
Additional sense code if the
value in the specified field
exceeds the maximum limit
COMPARE AND WRITE
CDB NUMBER OF
LOGICAL BLOCKS field
MAXIMUM COMPARE AND
WRITE LENGTH field
INVALDIN FIELD IN CDB
ORWRITE (16) / (32)
CDB TRANSFER
LENGTH field
MAXIMUM TRANSFER
LENGTH field
PREFETCH (10) / (16)
CDB PREFETCH
LENGTH field
MAXIMUM PREFETCH
LENGTH field
READ (10) / (12) / (16) / (32)
CDB TRANSFER
LENGTH field
MAXIMUM TRANSFER
LENGTH field
VERIFY (10) / (12) / (16) / (32)
CDB VERIFICATION
LENGTH field
WRITE (10) / (12) / (16) / (32)
CDB TRANSFER
LENGTH field
READ (10) / (12) / (16) / (32)
XDWRITEREAD (10) / (32)
XPWRITE (10) / (32)
Any individual block device range
descriptor in a POPULATE TOKEN
command (see SBC-4)
Block device range
descriptor NUMBER
OF LOGICAL BLOCKS
field
MAXIMUM TRANSFER
LENGTH field
INVALID FIELD IN
PARAMETER LIST
Any individual block device range
descriptor in a WRITE USING TOKEN
command (see SBC-4)