Write Record Zero
Hex Code
Data Address
Count
15
The main storage location of the R0 count, key
and data bytes.
16
Description:
The Write Record Zero command formats a new record zero on the
track. Record zero is always the first record following the home address area. The
first 8 bytes of the record transferred from the channel are the count area: cylinder
number (2 bytes), head number (2 bytes), record number (1 byte), key length (1
byte), and data length (2 bytes). The remaining 8 bytes are the data area.
The control unit requests an 8 byte count area from the channel. The key and data
area lengths are defined in the count area. If the channel sends a count field of
fewer than 8 bytes, the operation is rejected with unit check. The sense data
contains command reject with format 0, message 3. The area must define a
standard R0 with the following restrictions:
The CCHH specified must be equal to the currently addressed cylinder and
track.
The R value specified must be zero.
The Key Length (KL) must be zero.
The Data Length (DL) must be 8.
If any of these restrictions are violated, the operation is rejected with unit check.
The sense data contains command reject with format 0, message 4.
Record zero formats without a key area. If the channel sends fewer than (DL)
bytes, binary zeros fill the remaining bytes of the data area.
If this command is not followed by a Write CKD command, the remaining portion of
the track is erased.
Chaining and Restrictions:
Unit check status with the sense data containing
command reject with format 0, message 2 occurs if:
This command is not in a Locate Record or Locate Record Extended domain,
and is not preceded by either a Search Home Address command that
compares equal on all 4 home address bytes, or a Write Home Address
command not in a Locate Record or Locate Record Extended domain.
The file mask does not permit writing R0 (bits 0 and 1 not ‘11’).
This command is in a Locate Record or Locate Record Extended domain
specifying other than a Format Write (03) operation with home address
orientation (byte 0, bits 0 and 1 are ‘01’or ‘11’).
Ending Status:
If additional commands are expected within the domain of a
Locate, device end will be presented with channel end. Otherwise channel end will
be presented when the data transfer is complete to the cache. The control unit is
oriented to the record zero data area when the command completes.
Chapter 4. Command Descriptions
4-85
Содержание Multiprise 3000
Страница 1: ...S 390 Multiprise 3000 Enterprise Server R IBM Internal Disk Subsystem Reference Guide SA22 1025 00 ...
Страница 2: ......
Страница 3: ...S 390 IBM Internal Disk Subsystem Reference Guide SA22 1025 00 ...
Страница 32: ...2 12 Internal Disk Subsystem Reference Guide ...
Страница 38: ...3 6 Internal Disk Subsystem Reference Guide ...
Страница 182: ...4 144 Internal Disk Subsystem Reference Guide ...
Страница 198: ...5 16 Internal Disk Subsystem Reference Guide ...
Страница 214: ...6 16 Internal Disk Subsystem Reference Guide ...
Страница 234: ...A 10 Internal Disk Subsystem Reference Guide ...
Страница 238: ...B 4 Internal Disk Subsystem Reference Guide ...
Страница 243: ...4 lease the Code or any copy of it Appendix C Warranties C 5 ...
Страница 244: ...C 6 Internal Disk Subsystem Reference Guide ...
Страница 248: ...D 4 Internal Disk Subsystem Reference Guide ...
Страница 254: ...X 6 Internal Disk Subsystem Reference Guide ...
Страница 263: ......
Страница 264: ...IBM Printed in the United States of America on recycled paper containing 10 recovered post consumer fiber SA22 1 25 ...