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SCSI Commands
The Parameter Pointer Field
Log Pages
Field
Bytes
Bits
Allocation
7-8
7-0
Length
Reserved
Control
9
The Page Control (PC) field specifies the type of counters that the initiator is
requesting. The value 01b is the most common page control setting. This requests
the accumulated counts for the page to be returned. These counts reflect the current
count of events since the last power-on cycle, SCSI bus Reset, Bus Device Reset,
cartridge loading, or the last Log Select command that cleared the parameter values.
Accumulated values are incremented by the drive as an event occurs. For pages
02h, 03h, and 32h, these values can be cleared with all the above methods. For
page 0Ch these values can be cleared with all the above methods except with Log
Select.
Because the drive maintains the accumulated values in volatile memory, the values
may be lost if a power cycle occurs.
The PC field is ignored for pages 00h, 0Ch, 2Eh, 30h, and 31h and the accumulated
values are always returned except page 00h which has no accumulated values.
The Parameter Pointer field specifies the starting page that is to be transferred.
For example, if the page uses parameter codes 2 through 6 and the parameter
pointer field is set to 3, then the drive returns parameters 3 through 6. Likewise, if the
parameter pointer is set to 1, parameters 2 through 6 are returned.
If the Parameter Pointer field is set to 0, all parameters for that particular page are
returned up to the maximum number of bytes specified in the allocation length.
Regardless of the starting parameter code specified in the Parameter Pointer field,
the page header is always returned.
There are several logs of different formats that allow you to retrieve different drive
parameters. The following logs are supported:
Log
Supported Log Pages Log
Write Error Counters Log
Read Error Counters Log
Sequential Access Device Log
Tape Alert Log
Description
The Allocation Length field specifies the maximum amount of mem-
ory space (in bytes), which the initiator has reserved for Log Sense
data.
The drive returns the number of bytes contained in the requested
page, or the requested Allocation Length, whichever is less. If the
Allocation Length is less than the actual page length, the transfer is
truncated.
All reserved bits must be 0.
See Control Byte Format on page 18.
See Page
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