
command is rejected with unit check status. The sense data contains command
reject with format 0, message 4.
Notes:
1. Extent checking is performed during the validation of Locate Record Extended
parameters, not during track access.
2. The sector number parameter is not used.
Track access is initiated using the seek address parameter.
When track access is complete, the control unit orients to the beginning of the
count area of a user record and prepares to transfer the associated record. The
search argument is ignored and no search operation is performed. If no data is
found in the accessed track, the operation is rejected with unit check status. The
sense data includes No Record Found.
When auxiliary byte, bit 7 is ‘0’, Locate Record Extended must be followed by a
sequence of multitrack Read Count, Read Count Key and Data, or Read Data
commands sufficient to process the specified number of records in the count
parameter. When the auxiliary byte bit 7 is ‘1’, the last channel command in the
Locate Record Extended domain must be a multitrack Read Count command.
If an invalid command sequence is detected within the Locate Record Extended
domain, the invalid command will be rejected with unit check status. The sense
data contains command reject with format 0, message 2.
If the operation continues past the last record on a track, the control unit orients to
the beginning of the count area of the first data record on the track and prepares to
operate on that record.
If the number of read commands exceeds the number of data records on the track,
one or more of the data records will be read again. No exception is reported.
The record ID of the first record is contained in the first count field, or can be found
by suffixing a Read Count command to the Locate Record Extended domain.
If the number of records read is equal to the number of data records on the
track, the count area read by a suffixed Read Count command is that of the
first record that was read.
If the number of records read is not equal to the number of data records on the
track, the count area read by a suffixed Read Count command will be that of
the record that follows the last record read. The ID of the first record read is
determined by referencing the record ID read, and the known sequence of the
record IDs on the track.
Write Any – ‘09’ Extended Operation Code:
This operation code prepares the
control unit to write a specified number of data records to a track 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.
Chapter 4. Command Descriptions
4-35
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