Fujitsu M2488 manual Early Warning Indication, Deferred Write Errors, Additional Information

TAPE UNIT SCSI COMMANDS M2488 PRODUCT GUIDE

It is possible for the value in the information bytes of the sense data generated when a CHECK CONDITION is returned for a WRITE command to exceed the transfer length specified in the CDB of the WRITE command.

Early Warning Indication:

If a WRITE command is received while the logical unit is positioned after the early-warning indi- cation (but before physical EOM), the target continues to operate in the current Buffered Mode as indicated in the mode parameters (reference MODE SENSE/SELECT data header) using the buffer size indicated by the Buffer Size at Early-Warning mode parameter (reference MODE SENSE/SELECT page 10h). The target also returns a CHECK CONDITION status for each of these WRITE commands. If all of the data is successfully transferred into the buffer and physical EOM has not been encountered, the sense key is set to NO SENSE, the valid and EOM bits are set to one, and the information bytes are set to zero. If physical EOM is encountered, the sense key is set to VOLUME OVERFLOW, the EOM bit is set to one, the valid bit is set to one, and the value of the information bytes are as described above.

Deferred Write Errors:

A deferred write error condition occurs when the target detects an error has occurred on a buffered WRITE command that previously reported GOOD status. This condition persists until one of the following occurs:

1)The deferred error is reported and the buffered data is recovered by the initiator via the Recover Buffered Data command.

2)The deferred error is reported and the buffered data is discarded by the initiator via the Rewind or Load/Unload command.

3)A BUS DEVICE RESET message is received from any initiator.

4)A hard reset condition is detected by the target.

If a deferred write error occurs while operating in Buffered Mode 1 (data from multiple initiators can reside in the buffer at once), the deferred write error is reported to the first initiator issuing the next command if other than INQUIRY or REQUEST SENSE. If a deferred write error occurs while operating in Buffered Mode 2 (the buffer can contain data from only one initiator), the error is reported to the initiator with unwritten data in the buffer. All other initiators receive BUSY sta- tus until the deferred error condition is cleared.

Additional Information:

The target ensures that some additional data can be written to the medium (e.g. filemarks) after the first EOM indication has been returned to the initiator.

The data written to the tape is written in EDRC compressed format depending on the Select Data Compression Algorithm field in the Mode (SENSE/SELECT) parameters, Mode Page 10h. See the description of the Mode SENSE/SELECT parameters for more information on the compression mode based on these items.

This device writes all data to tape in 36-track format. Therefor, if an attempt is made to write over 18-track data away from BOT, CHECK CONDITION status is generated. The sense key is set to MEDIUM ERROR and the additional sense code is set to INCOMPATIBLE MEDIUM INSTALLED.

4-142 CG00000-011503 REV. A April 1997