User's Guide

Commands: Log Sense (4Dh) Page 57
LOG SENSE (4Dh)
The LOG SELECT and LOG SENSE commands are used in conjunction with each
other. These commands allow the host to obtain and control statistical information.
This information consists of counts related to particular events that occur.
Some tabulated events (page 3) refer to errors that have occurred since the Mini-
cartridge drive was powered on or last cleared by a LOG SELECT command and
that have accumulated across several backup or restore operations on several
cartridges.
The vendor unique page 30 contains statistical information that is DDS specific. This
DDS information is contained in the Tape Log area on each tape or partition. This
protected reference data is tabulated and maintained for the particular tape currently
being used.
For pages 2 and 3, the LOG SELECT command is used to preset counts to a
specific value or to reset the counts if the maximum count is reached. The log sense
data is reset on a SCSI Bus Reset or a Bus Device Reset.
Log sense data is obtained by specifying a log page in the Page code field of the
LOG SENSE CDB. Only one page of data can be requested by the host of each
LOG SENSE command. The pages used by the drive are found by reading Log
Page 0. Any request for unused pages causes a Check Condition. The sense data
are then set to Illegal Request, Invalid Field in the CDB.
LOG SENSE Command Descriptor Block
The following table shows the layout of the CDB.
Byte
Bits
7 6 5 4 3 2 1 0
0 0 1 0 0 1 1 0 1
1 0 0 0 0 0 0 0 0
2 PC | Page Code
3 0 0 0 0 0 0 0 0
4 0 0 0 0 0 0 0 0
5 MSB—Parameter Pointer
6 Parameter Pointer—LSB
7 MSB—Allocation Length
8 Allocation Length—LSB
9 vendor unique* 0 0 0 0 Flag Link
* This vendor-unique field is reserved and must be set to zero.