Device Release
Description:
The Device Release command transfers 32 bytes of sense data to
the channel.
If the logical volume is busy or reserved to another LPAR, the Device Release
command is I/O queued. Internal Disk queues CCW chains using a FIFO queue
discipline. While the chain is queued, the channel emulator in Internal Disk
maintains the subchannel in a Start Pending state. If the logical volume is not
busy, the Device Release command operates even if the logical volume is not
ready, or of the physical drive is busy. See “Effect of Subsystem and Device State
on Status Presented to Command” on page 2-5 for the operation of this command
when other subsystem and device status conditions occur.
The Device Release command includes all the Sense command functions. It
causes the reservation of the logical volume to terminate for the LPAR sending the
command.
When a Device Release command is sent to a logical volume in the contingent
allegiance state, much logical volume status testing normally done during initial
selection is bypassed. This is so the control unit can present zero initial status and
report the error information from the last unit check. The Sense, Device Reserve,
Device Release, and Unconditional Reserve commands bypass the normal logical
volume status testing.
Chaining and Restrictions:
Unit check status with the sense data containing
command reject with format 0, message 2 occurs if:
This command is received in the domain of a Locate Record or Locate Record
Extended command.
This command is preceded in a channel program by a Define Extent or a Set
File Mask command.
On a 3390 logical volume, this command is preceded in a channel program by
a Read IPL command.
Ending Status:
The control unit presents channel end and device end after data
transfer completes.
Hex Code
Data Address
Count
94
The main storage location for the first sense byte.
32
4-120
Internal Disk Subsystem Reference Guide
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