CDB fields:

Code

The Code field indicates what is to be spaced to:

 

000

Blocks—The number of blocks crossed is dictated by Count.

 

001

Filemarks—The number of filemarks crossed is dictated by Count.

 

011

EOD—Space to the end of data in the current active partition.

Count

• When spacing over blocks or filemarks this field indicates how many blocks or

 

marks should be crossed. Spacing is forward (towards EOM) unless Count is

 

negative (twos complement) when the spacing is towards BOM.

 

• When spacing to EOD the Count field is ignored.

 

• When not spacing to EOD, if Count is zero, the SPACE command is treated as a

 

null operation. The logical position remains unchanged, and unwritten data is not

 

flushed to tape.

 

 

Parameter Length

0 Explicit block mode is not supported.

 

 

Space specific status:

If the drive fails to space either from a medium error or from some sort of non-fatal drive error, CHECK CONDITION status is reported. The sense key will be set to MEDIUM ERROR. Additional sense depends on the nature of the error. The two most common additional sense code and qualifiers in this case will be: 1100h (unrecovered read error) and 3B00h (sequential positioning error).

The drive implements the following priority scheme when a tape position point is encountered:

Lowest priority

Blocks

 

 

Filemarks

If the drive meets a filemark while spacing to a block CHECK CONDITION is

 

 

reported. The Mark bit in the sense data is set, and the sense key is NO

 

 

SENSE. Additional sense is 0001h (filemark encountered). The final

 

 

position will be before or after the filemark depending on whether the

 

 

space was reverse or forward.

 

EOD

If the drive meets EOD while spacing to a block or mark, CHECK

 

 

CONDITION is reported. The EOM bit in the sense data is set. The sense

 

 

key is BLANK CHECK and additional sense is 0005h (EOD encountered).

 

BOM

If the drive meets BOM while spacing, CHECK CONDITION is reported. The

 

 

EOM bit and Valid bit in the sense data are set to 1 and the information

 

 

bytes set to the total number of blocks or filemarks that remain to be

 

 

spaced over (in other words, the requested number minus the number that

 

 

have been spaced over). The sense key is NO SENSE and additional sense

 

 

is 0004h (BOT detected).

Highest priority

EOM

If the drive meets EOM while spacing, CHECK CONDITION is reported. The

 

 

EOM bit in the sense data is set. The sense key is MEDIUM ERROR and

 

 

additional sense is 0002h (EOP/M detected).

•If “blank media” is encountered during a space (in other words, the drive attempted to space on an unformatted tape), the drive behaves as if EOD was at BOM. It will then

Commands

SPACE 11h 173