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LOG SENSE 4Dh
Commands
69
Performance Data log page
The Performance Data log page is 34h. This log is intended to report data of interest to a user/
application on how efficiently the drive is being used.
The Parameter Control Byte is 60h for all the parameters.
All the parameters relate to the current tape. They are all cleared at the start of tape load, except
Parameter 4, which is never cleared. All data will be reset when the log page is reset. The
parameters are as follows.
Parameter Description Length Updated
0 Repositions per 100 MB 2 After each 100 MB has been physically written
1 Data rate into buffer 2 After each data set has been logically written
2 Maximum data rate 2 After each data set has been logically written
3 Current data rate 2 After each data set has been logically written
4 Native data rate 2 Fixed
Repositions per 100 MB Number of tape direction changes per 100 MB written. The higher the figure the more
wear occurs.
Data rate into buffer Rate at which data is entering the buffer (after data compression), given in units of
100 KB/s. This is the true ‘tape’ data rate.
Maximum data rate Given the compressibility of the data that has been sent to the drive, this is the
maximum data rate that could be achieved, given in units of 100 KB/s. The figure is
calculated based on the compressibility of each dataset received, and datasets that
have a compressibility greater than the compression bandwidth of the drive will be
‘capped’.
Current data rate Rate at which data is being accepted by the drive before compression, given in units of
100 KB/s.
Native data rate The native rate (that is, without using compression) at which the drive writes data to
tape, given in units of 100 KB/s:
Drive Value Native Data Rate
Generation 1 full-height
Generation 1 half-height
Generation 2
Generation 3
96h
4Bh
12Ch
230h
15 MB/s
7.5 MB/s
30 MB/s
80 MB/s
NOTE: These figures are for
native media types and will
vary when earlier format
media is loaded