Sony SDX-700C, Product Specifications Manual

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6.Command Specification LOG SENSE
6-30 SONY AIT-3 drive SDX-700 series Ver.2.1
Kilobytes to/from Data Compression : The total number of kilobytes written to or read from the tape since the last
power-on or Clear Log operation. For Kilobytes from Data Compression, this number may be greater than the
number of kilobytes transferred to the host due to read ahead.
Logical Entity Size : The logical size of the last entity written to or read from the tape: size = number of record in
entity × record size in bytes
Physical Entity Size : The physical size of the last entity written to or read from the tape: size = entity header length
+ uncompressed data length
Uncompressed Entities : The total number of times non-ALDC entities have been encountered on the tape during
read operations since the last power-on or Clear Log operation.
LOG SENSE Commands : From these figures, the host can calculate the average compression ratio achieved by
the autoloader since the last power-on or Clear Log operation as follows:
Average_compression_ratio = Kilobytes_to_data_compression / Kilobytes_to_tape
Similarly, the host can calculate instantaneous compression ratio achieved by the autoloader for a particular read or
write command:
Instantaneous_compression_ratio = Logical_entity_size / Physical_entity_size
6.6.12. AIT Log Page (3Ch)
This page is for the AIT original Tape Log. The AIT Tape Log of each fields are larger than legacy Tape Log Page.
The legacy Tape Log Page returns the part of AIT original.
6-28: AIT Log Page
Bit
Byte
7 6 5 4 3 2 1 0
0 Page Code (3Ch)
1 Reserved
2 (MSB) Page Length (n+1)
3 (LSB)
Bit
Byte
7 6 5 4 3 2 1 0
0 (MSB) Parameter Code (0001h - 0012h and 0101h - 0112h)
1 (LSB)
2 DU(0) DS(1) TSD(0) ET(0) TMC(00)
Reserved
LP(0)
3 Parameter Length (n-3)
4 (MSB) Parameter Value
N (LSB)
Previous Groups Written : This is the number of groups physically written to the tape or partition since the last
update of the System area. Where Repeat Writing is in force, this count increments for each instance.
Total Groups Written : This is the total number of groups physically written to the tape or partition since the first time
the tape or partition was written. The number accumulates over the life of the tape but is ZEROed by a format pass.
Where Repeat Writing is in force, this count increments for each instance.
Previous Groups Read : This is the number of groups physically read from the tape or partition since the last update
of the System area.
Total Groups Read : This is the total number of groups physically read from the tape or partition since the first time
the tape or partition was written. This does not include any reading as part of a Read-After-Write check. The number
accumulates over the life of the tape but is ZEROed by a format pass.
Total Rewritten Frames : This is the total number of frames on the tape or within the partition that were needed to be
rewritten since the tape or partition was first written. It is incremented by 1 each time a frame is repeated following
error detection by the Read-After-Write process. This count does not include any frames which are written between
the original frame and its rewrite. The number accumulates over the life of the tape but is ZEROed by a format pass.