IBM Multiprise 3000, Reference Manual, Page: 121 / 264

Write commands that do not operate in a Locate Record or Locate Record
Extended domain must be preceded by a search command that compares equal on
all bytes of the search field. The Locate Record Orient operation code does not
satisfy the search prerequisite for a write command.
No write command is defined for both single-track and multitrack forms. Write
Count, Key, and Data Next Track, Write Update Key and Data, and Write Update
Data are defined for multitrack form only. All other write commands are defined for
single-track form only.
Track Padding
Track padding fills out the remaining portion of a track with a special byte pattern
after format writing completes. Track padding begins after the gap following the
last field formatted on a track.
If a command other than a format write is chained from a format write and device
padding is used, the command can operate as a command that is not oriented.
That is, device padding does not establish index orientation. Therefore, if the
channel reconnects after index, the next command operates whenever reconnection
occurs.
Record Padding
If the CCW byte count for any write command is less than that required to fill the
record areas operated on by that command, the remainder of the record will be
filled with binary zeros if no exception condition (other than incorrect length
indication) is detected. If any other exception condition causes data transfer to be
terminated prematurely, any data received for the affected record is discarded and
that record is not formatted or updated.
Invalid Track Format
An attempt to write a record beyond the end of a track will result in Invalid Track
Format being reported in sense data following unit check status to the offending
write command.
Chapter 4. Command Descriptions
4-83