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Data Compression Characteristics mode page fields:
DCE Data Compression Enable. This bit controls whether the drive uses compression when
writing. The value has no meaning when reading, that is, if the tape contains
compressed data, decompression will occur regardless of the setting of this bit.
The bit is analogous to the Select Data Compression Algorithm field on the Device
Configuration mode page (see page 81).
0
1
Compression is disabled
Compression is enabled
DCC Data Compression Capable
Read only. It will have the value of 1, indicating that compression is supported.
DDE Data Decompression Enable
Read only. It will have the value of 1, indicating that compression is enabled.
RED Report Exception on Decompression
Read only. It will have the value 0, meaning that the drive returns CHECK CONDITION
status when it encounters data that cannot be decompressed. This applies when data
has been compressed with an unknown or unsupported compression algorithm.
Compression
Algorithm
This indicates which compression algorithm will be used to process data from the host
when the DCE bit is set to one. If the host selects an algorithm which the drive does not
support, CHECK CONDITION is returned, with a sense key of ILLEGAL REQUEST. Only
the default algorithm (ID 1) is supported.
Decompression
Algorithm
This will also always be 1, indicating that the default decompression algorithm should
be used.