Quantum DAT 24 Drive Guía de usuario descargar pdf (Pagina 118)

Page 106 DDS-4 SCSI Interface Manual, Rev. B

Description of the READ Command

The READ command is complete when one of the following conditions is met.

These conditions are described in the following paragraphs.

• End-of-Data (EOD) is reached.

• A filemark (FM) is read.

• Transfer length is satisfied

• End-of-Tape (EOT) or end-of-partition (EOP) is reached.

• Unrecoverable data error occurs.

• Detection of incorrect block length.

End-of-Data

If EOD is encountered, the command terminates with a Check Condition status and

a Sense Key of 08h. If the Valid bit (byte 0, bit 7) is set indicating a residual count,

the Residual length field is determined as follows:

• If the Fixed bit is 1, it equals the difference between the CDB transfer length and

the number of actual blocks read.

• If the Fixed bit is 0, it equals the CDB transfer length.

The tape is then positioned to allow an Append Data operation.

Filemark

If a filemark is encountered, the command terminates with a Check Condition, and

the filemark bit (byte 2, bit 7) of the sense data is set to 1. If the Valid bit (byte 0, bit

7) is set indicating a residual count, the Residual length field is determined as

follows:

• If the Fixed bit is 1, it equals the difference between the CDB transfer length and

the number of actual blocks read.

• If the Fixed bit is 0, it equals the CDB transfer length.

On termination, the tape is positioned after the filemark on the EOT side of tape.

Setmarks

If the RSMK bit in the Device Configuration Page parameter of the MODE SELECT

command is reset (0), Setmarks are ignored and skipped over.

If the RSMK bit is set (1) and a setmark is encountered, the command terminates

with a Check Condition. The Filemark bit (byte 2, bit 7) and the Valid bit (byte 0, bit

7) of the sense data are set.

The Residual Length field is then set as follows:

• If the Fixed bit is 1, it equals the difference between the CDB transfer length and

the number of actual blocks read.

• If the Fixed bit is 0, it equals the CDB transfer length.

On termination, the logical position is after the Setmark.

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Quantum DAT 24 Drive Guía de usuario Pagina 118