Quantum DLT 4000 Product Manual page 221

Active Partition
Only partition 0 is supported. Setting this field to any other value will be rejected by
the drive with a CHECK CONDITION status and the ILLEGAL REQUEST sense key
set.
Write Buffer Full Ratio and Read Buffer Empty Ratio
These indicate how full/empty the buffer memory should be before restarting the
writing/reading of the media. The DLT4000 drive will set these fields to zero (unused)
because it uses an automatic, adaptive mechanism to dynamically adjust its
Full/Empty ratios according to the average data rates over the SCSI bus.
Write Delay Time
This indicates the maximum time that the drive will wait with a partially full buffer
before forcing the data to tape (100 ms increments). The buffer Full/Empty ratio,
which is dynamic, can cause data to be written sooner than the Write Delay time
would indicate. The Write Delay Time defaults to 200 (C8h). This causes the buffer to
be flushed in 20 seconds. Maximum value is 6500 (1964h) and the minimum is 15
(0Fh). This represents delays from almost 11 minutes down to 1.5 seconds.
Values between 0 and 15, on a MODE SELECT, are rounded down to 0. This causes
the data to go straight to the media without delay.
Byte 8:
DBR - set to 0 (data buffer recovery not supported)
BIS - set to 1 (Block Identifiers Supported in media format)
RSmk - set to 0 (Setmarks not supported)
AVC - set to 0
SOCF - set to 0
RBO - set to 0
REW - set to 0 (Do not report Early Warning EOM on reads)
Gap Size
This field is not used and is set to zero.
EOD Defined
This field is set to 00h; any other value will be rejected by the drive.
EEG
The Enable EOD Generation bit is set to indicate that the drive will generate an EOD.
The drive generates an EOD mark before any change of direction following a write-
type operation. This bit is ignored on MODE SELECT.
DLT4000/DLT4500/DLT4700 Cartridge Tape Subsystem 8-61
DLT4000 SCSI Interface