Erase
Hex Code
Data Address
Count
11
The main storage location of the count, key,
and data bytes.
The number of count, key, and data bytes.
Description:
The Erase command erases one or more user data records from the
track. The remaining portion of the track is erased starting from the end of the
record written by the preceding Write R0 or Write CKD command, or from the end
of the record that satisfied the Search ID Equal or Search Key Equal operation.
This command operates like a Write CKD command. However, instead of
formatting a record on the track, it discards the channel data. The remaining
portion of the track is erased, starting from where a Write CKD command would
start writing.
The first 8 bytes are like a count area. The key length and data length fields
specify the number of additional bytes to transfer. The control unit requests an
8-byte count area from the channel. If the channel sends fewer than 8 bytes,
binary zeros fill the remaining bytes and the operation continues, using zeros for
the fields not transferred. The key and data area lengths are defined in the count
area. If the channel sends fewer than (KL) + (DL) bytes, data transfer ends.
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 a Locate Record or Locate Record Extended
that does not specify a Write Track (0B) operation.
This command is not in the domain of a Locate Record or Locate Record
Extended, and is not preceded by either:
– A Search ID Equal or Search Key Equal command that compares equal on
all bytes of the ID or key field, or
Note:
A Read Key and Data, Read Data, Write Key and Data, or Write
Data command can be between the Search ID Equal and the Erase
command. A Read Data or Write Data command can be between
the Search Key Equal and the Erase command.
– A Write Record Zero or Write CKD command that executed outside of the
domain of a Locate Record or Locate Record Extended.
The file mask inhibits format write operations (bits 0 and 1 are ‘01’ or ‘10’).
If the track does not have enough space for the record, the command is terminated
with unit check status. The sense data includes Invalid Track Format. The residual
byte count in the channel status information may not show the amount by which the
record length exceeded the available space on the track.
Ending Status:
Channel end and device end status occurs when the logical
volume completes the erase operation.
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Internal Disk Subsystem Reference Guide
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