
The data field bytes are all equal to zero.
If Bit 5 is set to zero, the Record Zero differs from the above only in the data field
content. The data field bytes are those that are provided in the parameters of the
Write Record Zero command. Therefore, the Data field bytes may or may not be
equal to zero.
Beginning of Extent Address – Bytes 8 through 11
Bytes 8 through 11 contain the address (CCHH) of the first track in the extent.
(“Define Extent Command” on page 3-3 describes an extent.) CCHH must be a
valid track address for the logical volume.
If (CCHH) is not a valid track address, the command is rejected with unit check
status. The sense data contains command reject with format 0, message 4. See
Appendix A, "Device Characteristics" on page A-1 for valid track address ranges.
End of Extent Address – Bytes 12 through 15
Bytes 12 through 15 contain the address (CCHH) of the last track in the extent.
(CCHH) must be equal to or greater than the (CCHH) value specified by the
“beginning of extent address” in bytes 8 through 11. The track address must be
valid for the access authorization and logical volume type. (See “Beginning of
Extent Address – Bytes 8 through 11” for the valid requirements.)
If (CCHH) is not a valid track address, or the (CCHH) is less than the value in
bytes 8–11, the command is rejected with unit check status. The sense data
contains command reject with format 0, message 4. See Appendix A, "Device
Characteristics" on page A-1 for valid track address ranges.
Locate Record
Description:
The location and number of records to process and the operation to
perform are specified in the Locate Record command parameters. See “Locate
Record and Locate Record Extended Commands” on page 3-3 for how the Locate
Record command makes an operational domain. See “Locate Record Operations”
on page 4-18 for the specific Locate Record operation.
The Locate Record command resets orientation in the control unit. This command
establishes the orientation state specified by the operation byte parameter before
any data transfers to or from the logical volume.
Chaining and Restrictions:
Unit check status with the sense data containing
command reject with format 0, message 2 occurs if:
This command is in the domain of another Locate Record, or Locate Record
Extended.
A Define Extent or Read IPL command does not precede this command in the
same channel program.
The control unit requests 16 bytes of parameters from the channel. If the channel
sends fewer than 16 bytes, the command is rejected with unit check status. The
sense data contains command reject with format 0, message 3.
Hex Code
Data Address
Count
47
The main storage location of the first parameter byte.
16
Chapter 4. Command Descriptions
4-13
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