Quantum 1200 Series DAT Autochanger Podręcznik Użytkownika Pobierz pdf (Strona 282)

SPACE Command (11h) SDLT 600 SCSI Interface Guide

4-240 January 2005 81-81200-02 REV A01

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 BOM / 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 or BOM / BOP.

Depending on the size of blocks, read ahead data in the buffer allows some spacing requests to be

satisfied without actual tape movement.

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.

Table 4-141. SPACE Command Data — Field Descriptions (Continued)

Field

Name Description

1 2 ... 277 278 279 280 281 282 283 284 285 286 287 ... 293 294

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Quantum 1200 Series DAT Autochanger Podręcznik Użytkownika Strona 282