Reference Guide

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 nth 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 nth 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 nth 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 nth
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.