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Quantum DLT 7000 Tape System 5-81
MODE SELECT (6) / (10) Command (15h) / (55h) (continued)
Table 5–43 Data Compression Page Descriptor - Field Descriptions
Field Name Description
Page Code The Page Code identifies the type of MODE SELECT page being transferred. A
value of 0Fh identifies this as the Data Compression page.
Page Length The Page Length field indicates the number of bytes in the Data Compression
page that follow this byte. The valid value for this byte is 0Eh.
DCE Data Compression Enable. This bit specifies whether the tape drive should
enable or disable data compression. When set to 1, the drive starts in
compressed format.
DCC Data Compression Capable. This bit is used by the MODE SENSE command to
indicate that the tape drive supports data compression.
DDE Data Decompression Enable. Must be set to 1. When the tape drive reads
compressed data from tape, it automatically decompresses the data before
sending it to the initiator. Data compression must always be enabled.
RED Report Exception on Decompression. The tape drive does not report exceptions
on decompression (boundaries between compressed and uncompressed data).
The RED field must be 00h.
Compression
Algorithm
The Compression Algorithm field indicates which compression algorithm the
tape drive will use to process data from the initiator when the DCE bit (byte 02,
bit 7) is set to 1. The only value currently supported for this field is 10h.
NOTE: Specifying a value other than 10h for this field causes the tape drive to
return CHECK CONDITION status, sense key set to ILLEGAL REQUEST. However, if
EEPROM parameter EnaRepDecomp is set, the parameter in this field is ignored
and no CHECK CONDITION status is returned.
Decompression
Algorithm
The Decompression Algorithm field indicates which decompression algorithm
the tape drive will use when decompressing data on the tape. The only value
currently supported is 10h.
NOTE: Specifying a value other than 10h for this field causes the tape drive to
return CHECK CONDITION status, sense key set to ILLEGAL REQUEST.