Chapter 4 SCSI Commands
SPACE Command (11h)
DLT-S4 Interface Reference Guide
332
Table 188
SPACE
Command
Data
—
Field Descriptions
A
SPACE
command in the form “
SPACE
n
blocks” halts with
GOOD
status
after the
n
th block, or with
CHECK CONDITION
status on any occurrence of
Filemark, EOD, or BOP. A SPACE command in the form “SPACE
n
Filemarks” halts on the
n
th Filemark with
GOOD
status or with
CHECK
CONDITION
status on any occurrence of EOD.
Depending on the size of blocks, read ahead data in the buffer allows
some spacing requests to be satisfied without actual tape movement.
Field
Description
Code
The code can be one of the following values. All other values are reserved.
Space Code
Space By
0000b
Logical Blocks
0001b
Filemarks
0010b
Sequential Filemarks
0011b
End-of-Data
Count
When spacing over Blocks or Filemarks, the Count field is interpreted as follows:
• A positive value
n
causes forward motion over
n
blocks or filemarks. The drive logically
positions the tape after the
n
th Block or Filemark on the EOM or EOP side.
• A value of 0 causes no change in logical position.
• A negative value -
n
(two’s complement notation) causes reverse movement over
n
Blocks
or Filemarks. The drive logically positions the tape on the BOM or BOP side of the
n
th
Block or Filemark.
• When spacing to End of Data (EOD), the drive ignores the Count field. Forward
movement occurs until the drive encounters EOD. The position is such that a subsequent
WRITE
command appends data after the last object that the drive has written to tape
before EOD.