Locate; Command Description - Tandberg Data SLR7-140 PROGRAMMER Manual

11.
Logical LOCATE
Command
Physical LOCATE
Command

Locate

11.1. Command Description

The LOCATE command causes the Drive to position the tape
to a specified
physical and logical positions are supported.
The logical LOCATE command does not need special keys to
get to a certain logical position. The Block Address in
the CDB will for this command be interpreted as the
logical block position, meaning the number of blocks
seen on the SCSI-bus
position can be read by the READ POSITION command.
When using a SLRtape140 to SLRtape7 or SLR32 medium,
tapemarks on the tape count as one logical block each.
When using other tape media, tapemarks are not counted
as logical blocks.
The usage of the physical LOCATE is only legal when
using SLR5 or
(physical LOCATE is not supported by the SLR140, SLR100,
SLR75, SLR60 and
command will interpret the Block Address in the CDB as a
special key or " bookmark" . All blocks and tapemarks
can be identified with such a key. This position key can
be obtained with the use of the READ POSITION command.
While writing (or reading), the READ POSITION command is
typically executed every time the tape is at a position
that the Host system might want to go back to at a later
stage. The returned position key can then be stored and
used later as an input to the LOCATE command. These
values can be regarded as keys that are unique to any
given physical position on the tape. It might, however,
be several keys that will result in the same logical
position, as some physical tape blocks do not have any
logical contents (i.e. ECC blocks or Filler blocks). The
physical position numbers must be obtained with the READ
POSITION command, and must not be manipulated in any way
by the Host system. The LOCATE command will then bring
the tape back to the same position as it was when the
READ POSITION command was executed.
If a physical LOCATE command is issued to an ECC block,
the drive will position the tape to the next physical
data block.
If a physical LOCATE command is issued to a filler
block, the drive will position the tape to the next
physical data block.
If a physical LOCATE command is issued to an ID block,
the drive will position the tape to the next physical
data block.
If a physical LOCATE is issued into a Data Compression
Unit block, the drive will position the tape at the next
Data Compression Unit block.
11-1 Tandberg SLR Product Line SCSI Functional Specifications
position in the
from BOP.
DC9250 type media
SLR7 drives).
data stream.
The current logical
on SLR50 drives
The physical LOCATE
Both