Table
4-16. Extended Operation Code Length
Extended Operation Codes
Length
Write Any (09)
X
'
0001
'
Read Any (0A)
X
'
0001
'
Read Trackset (0E)
X
'
0001
'
or
X
'
0002
'
Prestage Trackset (10)
X
'
0001
'
or
X
'
0002
'
Write Trackset (11)
X
'
0001
'
or
X
'
0002
'
Update Write Trackset (13)
X
'
0001
'
or
X
'
0002
'
Extended Parameter – Bytes 20–21
This is a variable length field. Bytes in this field are requested from the channel
only if byte 0, bits 2–7 is X
'
3F
'
(Extended Operation), byte 17 specifies an
Extended Operation code that requires additional parameter bytes, and bytes
18–19 specifies an Extended Parameter length consistent with the byte 17
Extended Operation code. The number of bytes to be requested is specified in
bytes 18–19.
The extended parameter field, either byte 20 or bytes 20 and 21 as required,
contain data to support the processing of data transfer commands with the Locate
Record Extended domain.
Locate Record Extended Operations
The following text describes the Locate Record Extended command processing. It
also describes processing related to the data transfer commands that follow the
Locate Record Extended command. The command descriptions show the
processing that occurs as part of each data transfer command.
This section describes only those operations unique to the Locate Record Extended
command. For a general operations description and operation codes common with
Locate Record, refer to “Locate Record Operations” on page 4-18.
Read Any – ‘0A’ Extended Operation Code:
This operation code prepares the
control unit to read a specified number of data records from a ‘set of tracks’ without
first orienting to a specific record. No search operation is performed. The number
of records transferred is specified by the count parameter.
The extended parameter length (bytes 18–19) must equal X
'
0001
'
, otherwise the
command is rejected with unit check status. The sense data contains command
reject with format 0, message 4.
The extended parameter field must be one byte in length (byte 20 only). This byte
specifies the track set size used in the Locate Record Extended domain. The track
set size must be ‘1’ (the device value returned in byte 47 of the Read Device
Characteristics command response). If the track set size byte is other than ‘1’, the
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