Quantum Instruments DLT 7000 manual Space Command 11h, Eod

SCSI Commands

SPACE Command (11h) (continued)

Table 5–80 SPACE Command Data - Field Descriptions (continued)

Field Name	Description
Count	When spacing over blocks or marks, the Count field is interpreted as follows:
	A positive value N causes forward motion over N blocks or marks. The tape is
	logically positioned after the Nth block or mark 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 marks. The tape is logically positioned on the BOM or BOP side of the
	Nth block or mark.
	When spacing to EOD, the Count field is ignored. Forward movement occurs until
	the drive encounters EOD. The position is such that a subsequent WRITE command
	would append data after the last object that has been written to tape before EOD.

When executing SPACE, the tape drive implements the following hierarchy:

Highest BOM/P or EOM/P

EOD

Filemarks

Lowest Blocks

Note that a “space sequential filemarks” is a space to the first occurrence of n filemarks written sequentially.

A SPACE command in the form “SPACE N blocks” will halt with GOOD status after the Nth block, or with CHECK CONDITION status on any occurrence of Filemark, EOD, BOM/P, or EOM/P. A command “SPACE N Filemarks” will halt on the Nth Filemark with GOOD status on any occurrence of EOD, BOM/P, or EOM/P.

Depending on the size of blocks, read ahead data in the buffer allows some spacing requests to be satisfied without actual tape movement.

5-164 Quantum DLT 7000 Tape System