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SONY SDT-10000/SDT-11000 DDS Tape Drive
6. COMMAND SPECIFICATION
Note a - The logical position is located on the EOM side of the mark if movement was in the forward direction and on the
BOM side of the mark if movement was in the reverse direction.
Note b - The Information field is set to the difference (residue) between the requested count and the actual number of
blocks, filemarks or setmarks spaced over.
Note c - The Information field will contain no residue count and therefore the Valid bit is not set.
Note d - The drive will only report that a Setmark has been detected while spacing over blocks or Filemarks, if it has
been configured through MODE SELECT to Report Setmarks. Otherwise, the drive will continue the space operation
and the presence of the Setmark will be transparent to the Host.
Note e - The tape is positioned such that a subsequent WRITE would append data after the last entity that has been
written to the tape before EOD.
Note f - The tape is physically positioned at BOM/P.
Note g - EOM is only reported when the physical EOM/P is encountered. The tape is physically positioned at EOM/P.
The DDS format limits the number of Filemarks or Setmarks that may be written on a tape to a maximum of 65,536 of
each. If the drive is requested to space to greater than this number of Setmarks, it returns a CHECK CONDITION status
with an ILLEGAL REQUEST sense key set.
The drive is able to space along tape at up to 200 times normal speed. This fast search capability is a feature of the drive
which allows it to speed up longer moves on the tape. It is not intended to be used for moves that do not go across several
groups. This is because searching takes the same amount of time as reading 16 groups (one group = 126600 bytes).
Therefore, an algorithm has been implemented inside the buffer firmware which makes the decision of whether or not to
utilize this capability.
The drive’s buffer holds up to eight (8) groups worth of data (since the data buffer is 1 MBytes). Therefore, a single
record (less than 1 MB in length) may be read and then backspaced over repeatedly without the tape moving since once
the record is within the buffer, no further information is required from the tape.
SPACE may return the following sense keys on a CHECK CONDITION:
NO SENSE: If a Filemark occurs while spacing over blocks, the Filemark and Valid bits in extended sense are set to
one. The Information bytes are set to the difference (residue) between the requested count and the actual number of
blocks spaced over (not including the mark).
If a Save-Set Mark occurs while spacing over blocks or Filemarks, nothing is reported unless the SDT-10000/SDT-
11000 has been configured through MODE SELECT to Report Save Set Marks.
If the Report Save-Set Marks configuration is enabled and a Save-Set Mark occurs while spacing over blocks or
Filemarks, the Valid bit and the Additional Sense keys in the Returned Sense data are set to indicate that a Save-Set
Mark has been encountered. The information bytes are set to the difference (residue) in the requested count and the
actual number of blocks or Save-Set Marks spaced over (not including the detected Save-Set Mark).
If End-of-Data is detected while spacing over blocks or marks, the Valid bit and the Additional Sense Keys in the
Returned Sense Data are set to indicate that an EOD mark has been encountered. The Information bytes are set to the
difference (residue) in the requested count and the actual number of blocks or marks spaced over.
If BOT is detected while spacing over blocks or marks in the reverse direction, the EOM bit is set in extended sense. The
Valid bit is set to one and the Information bytes to the difference (residue) between the requested count and the actual
number of blocks or Filemarks spaced over.
SPACE
Summary of Contents for DDS-4
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