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Orientation Modifiers: Byte 0, Bits 0 and 1 contain orientation modifiers that
specify the orientation to establish when the operation (bits 2 through 7) needs
orientation to a specific record or record area before data transfer starts.
Count Area '00' – specifies that data access for the CCW immediately following
the Locate Record command is to begin with the control unit oriented following the
count field of the record that satisfied the search operation. Therefore, that CCW
can process the key and data areas of the record that satisfied the search
operation.
Count area orientation is valid with all operation codes.
Home Address '01' – specifies that data access for the CCW that immediately
follows Locate Record is to begin with the control unit oriented to home address.
Home address orientation is valid with the Orient (00), Format Write (03), Read
Data (06), Read Tracks (0C), and Read (16) operations only. If bits 2 through 7
contain any other code when bits 0 and 1 are '01', the command is rejected with
unit check status. The sense data contains command reject with format 0,
message 4.
Data Area '10' – specifies that data access for the CCW immediately following the
Locate Record command is to begin with the control unit oriented to the data area
of the record that satisfied the search operation. Therefore, that CCW will not
process any areas of the record that satisfied the search operation.
Data area orientation is valid with the Orient (00), Write Data (01), Read Data (06),
and Read (16) operations only. If bits 2 through 7 contain any other code when
bits 0 and 1 are '10', the command is rejected with unit check status. The sense
data contains command reject with format 0, message 4.
Index '11' – specifies that data access for the CCW immediately following the
Locate Record command begins with the control unit oriented to index.
Index orientation is valid with the Read (16) operations only. If bits 2 through 7
contain any other code when bits 0 and 1 are '11', the command is rejected with
unit check status. The sense data contains command reject with format 0,
message 4.
Note: A real 3990 mod 2 allows index orientation with Read (16) operations and
one write command: Write Special HA. Internal Disk does not support the
Write Special HA command, therefore, index orientation is valid with only
Read (16) operations.
Operations Codes: Byte 0, Bits 2 through 7 specify the operation to be performed
in the Locate Record domain. Any operation codes not shown are invalid. When
the operation code is invalid, the command is rejected with unit check status. The
sense data contains command reject with format 0, message 4.
Note: All operations performed in the domain of a Locate Record command can
be performed in a Locate Record Extended command, except for Orient and
Read Data operations.
See "Locate Record Operations" on page 4-17 for a description of the operation
codes.
Chapter 4. Command Descriptions
4-15
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