IBM Multiprise 3000, Reference Manual, Page: 59 / 264

The control unit uses the seek address and sector number parameters to start track
access. When track access completes, the search operation specified by the
search argument and the orientation modifiers (byte 0, bits 0 and 1) is performed.
If the auxiliary byte bit 7 is ‘0’, the Locate Record command must be followed by
the number of update write commands specified by the count parameter. If bit 7 is
‘1’, the Locate Record command must be followed by the number of update write
commands that is one less than the value specified by the count parameter. Also,
the last update write command must be followed by a multitrack Read Count
command.
When count orientation is specified and one update write command is required, the
Locate Record command must be followed by one of the following commands:
Write Data
Write Update Data
Write Key and Data
Write Update Key and Data.
When more than one update write command is required, the Locate Record
command must be followed by a sequence of either Write Update Data or Write
Update Key and Data commands. Write Update Data and Write Update Key and
Data commands cannot both occur in the same Locate Record domain.
When data orientation is specified, the Locate Record command must be followed
by a sequence of either the Write Update Data or Write Update Key and Data
commands. Write Update Data and Write Update Key and Data commands cannot
both occur in the same Locate Record domain.
If the Internal Disk detects an invalid command sequence in the Locate Record
domain, the invalid command is rejected with unit check status. The sense data
contains command reject with format 0, message 2.
If a multitrack operation continues after the last record on a track, the control unit
advances to the next track, and updates the first user data record on the next track.
(See “Operations in the Domain of a Locate Record or Locate Record Extended” on
page 4-2.) If the next track does not contain a user data record, the command is
terminated with unit check status. The sense data includes No Record Found.
The transfer length factor (or the blocksize from a Define Extent command if no
transfer length factor was specified) must be equal to the actual record length of
the records to update. The actual record length is either the data length or the sum
of the key and data lengths, depending on if the following write commands specify
Write Data or Write Key and Data.
If the actual length of any record to update differs from the transfer length factor (or
blocksize) value, and CKD conversion mode is not specified (Define Extent global
attributes byte, bit 2 is ‘0’), the command is terminated with unit check status. The
sense data includes Invalid Track Format. Also, the record is not updated.
If the actual length of the record to be updated differs from the transfer length factor
(or blocksize) value, and CKD conversion mode is specified (Define Extent global
attributes byte 1, bit 2 is ‘1’), then:
If the record length is zero, no data is transferred to the logical volume. The
command is terminated with unit exception status.
Chapter 4. Command Descriptions
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