Quantum DLT 4000 Manual descargar pdf (Pagina 258)

SCSI Commands

5-158 Quantum DLT 4000 Tape Drive

WRITE Command (0Ah) (continued)

Table 5–78 WRITE Command Data - Field Descriptions

Field Name Description

Fixed The fixed bit specifies both the meaning of the Transfer Length field and

whether fixed-length or variable-length blocks are to be transferred.

When the Fixed bit is 0, Variable-length block mode is selected. A single block

is transferred from the initiator and is written to the logical unit beginning at

the current logical tape position. Upon successful termination, the tape is

logically positioned after this block (on the EOM/P side). The Transfer Length

specifies the number of bytes that the drive handshakes out from the initiator

as one block.

When the Fixed bit is 1, the Transfer Length field specifies the number of blocks

to be transferred to the host beginning at the current tape position. This form

of WRITE is valid only if the logical unit is currently operating in the Fixed Block

mode – when it has been instructed to use fixed-length blocks with MODE

SELECT. The current block length is the block length defined in the MODE

SELECT command. Upon termination, the tape is logically positioned after

these blocks.

Transfer Length This field contains the length of the data transfer in bytes or blocks depending

on whether Fixed or Variable block mode is selected.

When the Transfer Length is 0, no data is transferred and the current position

on the logical unit is not changed.

Exception Conditions

If End of Tape (EOT) is detected while writing, the tape drive finishes writing

any buffered data. The command terminates with CHECK CONDITION status.

Within the sense data, the EOM bit is set, the Sense Key is set to NO SENSE,

and the Additional Sense code and Additional Sense Code Qualifier fields are set

to EOM/P detected. The drive attempts to complete any subsequent writes,

returning a CHECK CONDITION status in each case.

If the tape drive encounters the physical End of Medium (EOM) when

attempting WRITE, a CHECK CONDITION status is returned. Within the sense

data, the EOM and Valid bits are set, and the Sense Key field is set to Volume

Overflow. The Information fields contain the residue count and the Additional

Sense code and Additional Sense Code Qualifier fields are set to EOM/P

Detected. The tape is physically positioned at EOM/P.

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Quantum DLT 4000 Manual Pagina 258