Tandberg Data SLR7-140 PROGRAMMER, Руководство пользователя

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27-1 Tandberg SLR Product Line SCSI Functional Specifications
27.
Space
27.1. Command Description
The SPACE command provides a variety of positioning
functions determined by a space code and a space count.
Both forward (toward end-of-media) and reverse (toward
beginning-of-media) positioning are provided.
The SPACE command allows the Initiator to space over
blocks, tapemarks (filemarks or setmarks), sequential
tapemarks, bad blocks or to End-Of-Data (EOD).
When spacing over blocks or tapemarks, the count
specifies the number of blocks or tapemarks to be spaced
over. When spacing N blocks or tapemarks in the forward
direction, the space will end on the end-of-media side
of the last block or tapemark spaced. When spacing N
blocks or tapemarks in the reverse direction the space
will end on the beginning-of-media side of the last
block or tapemark spaced.
When spacing over N sequential tapemarks, the count
specifies that the space will end at the first
occurrence of N or more consecutive tapemarks. The tape
will be logically positioned at the end-of-media side
(forward space) or at the beginning-of-media side
(reverse space) of the n'th tapemark.
Reverse space over sequential tapemarks is recommended
not to be used. The operation is time consuming and
causes a lot of shuffles on the tape.
When spacing to End-Of-Data (EOD) the Count field will
be ignored. This space function is always using the
“ fast seek” algorithm. After a successful space to EOD,
a subsequent WRITE (or WRITE FILEMARKS) command will
append data to the last recorded block.
When spacing over bad blocks the Drive will space over
an area of contiguous unreadable tape. The Count field
and the FAST bit are ignored for this operation. When
the space over bad block operation is executed, the
Drive will space over all bad blocks until the next good
logical block is found. If there are no bad blocks in
the buffer, the data position is unchanged.
The SPACE command is able to space over blocks written
in both fixed and variable length modes. The SPACE
command is able to automatically determine the block
type while spacing.
If disconnection is allowed, the Drive will disconnect
when executing this command.