User's Manual

DLT4000 SCSI Interface
8-124 DLT4000/DLT4500/DLT4700 Cartridge Tape Subsystem
8.4.25 WRITE (0Ah)
Bit
7 6 5 4 3 2 1 0
0 Operation Code (0Ah)
1 Logical Unit Number Reserved Fixed
2 (MSB)
Byte 3 Transfer Length
4 (LSB)
5 Unused Reserved Flag Link
Figure 8-79 WRITE CDB
WRITE transfers one or more blocks from the host to the current logical position.
When in Buffered Mode (see MODE SELECT), the tape drive reports a GOOD status
on WRITE commands as soon as this data block has been transferred to the data
buffer.
The drive flushes the write buffer to tape under the following conditions:
• The write hold-off time limit is exceeded. (See MODE SELECT command.)
• Receipt of the following nonwrite commands:
LOAD-UNLOAD
REWIND
ERASE
LOCATE
MOVE MEDIUM
PREVENT/ALLOW MEDIUM REMOVAL that clears a prevent state
• A Write Filemarks command with the immediate bit cleared.
• A SCSI Reset or Bus Device Reset a reset message is received
If Buffered Mode is not selected, the buffer will flush after every write-type command.
Buffered Mode can be configured through MODE SELECT, and if it is not used, the
tape drive suffers a significant degradation in performance with respect to transfer rate
and therefore, loss of streaming.