SCSI Log Select Command
Encyclopedia
The SCSI Log Select command "provides a means for an application client to manage statistical information maintained by the SCSI
target device about the target device or its logical units". The format of the CDB
for the Log Select command is:
The special parameter fields in the CDB have the following meaning:
SCSI
Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...
target device about the target device or its logical units". The format of the CDB
SCSI CDB
In SCSI computer storage, commands are sent in a Command Descriptor Block .Each CDB can be a total of 6, 10, 12, or 16 bytes, but later versions of the SCSI standard also allow for variable-length CDBs. The CDB consists of a one byte operation code followed by some command-specific parameters.A...
for the Log Select command is:
| bit→ ↓byte |
7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|---|
| 0 | Operation code = 4Ch | |||||||
| 1 | Reserved | PCR | SP | |||||
| 2 | PC | Page Code | ||||||
| 3 | Subpage Code | |||||||
| 4 | Reserved | |||||||
| 5 | ||||||||
| 6 | ||||||||
| 7 | Parameter list length | |||||||
| 8 | ||||||||
| 9 | Control | |||||||
The special parameter fields in the CDB have the following meaning:
- PCR - Parameter Code Reset - setting this bit instructs the target to reset all parameters to their default values
- SP - Save Parameters - setting this bit instructs the target to save all saveable log parameters to a non-volatile memory or media area
- PC - Page Control - specifies which data counter parameter values shall be processed:
- 00 - Threshold Values
- 01 - Cumulative Values
- 10 - Default Threshold Values
- 11 - Default Cumulative Values
- Parameter List Length - in bytes