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6.Command Specification
Entities Written/Read: The total number of complete entities written to or read from the tape since the last power-on
or Clear Log operation.
Records Written/Read: The total number of records(both compressed and uncompressed) written to or read from
the tape since the last power-on or Clear Log operation.
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.
Bit
7
Byte
0
1
2
(MSB)
3
Bit
7
Byte
0
(MSB)
1
2
DU (0)
3
4
(MSB)
N
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.
6-28
Table 6-27: AIT Log Page
6
5
Page Length (n+1)
6
5
Parameter Code (0001h - 0012h and 0101h - 0112h)
DS (1)
TSD (0)
Parameter Length (n-3)
4
3
Page Code (3Ch)
Reserved
4
3
ET (0)
TMC (00)
Parameter Value
SONY AIT-2 Turbo drive SDX-550V series Ver.1.0
LOG SENSE
2
1
0
(LSB)
2
1
0
(LSB)
LP (0)
Reserved
(LSB)
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