The address to which centrol is
returnedupon coapletion of operation to be
the
In addition, theIOBLOK contains status
flags that indicate the current state of
the operation (such as, whether or not an
error has occurred, if an errcr recovery (ERP) is in and the
condition returned fro. the510) and the CSW associated with the interrupt that
signals the end of the operation.Since IOBLOKS are queued off various I/O control
tlocks, they also contain forward and
backward queuepOinters. DMKIOS builds in thea the real device address of the unit on
which theoperation is started.
In general, theIOBLOK representing a
given operation progresses through the
systemby being queued, in turn, from device, control unit, and channel blocks
until a path is at last free to the device.
A510 is then issued. After the operation
is complete, theIOBLOK is dequeued fro.
theRDEVBLOK and stacked on a queue maintained in the dispatcher, D!KDSP. Each tiae the dispatcher is entered, the entries
on the queue are unstacked and control is
passed to the pointsFecified in the
Interrupt Return Address(IOEIBA). After
I/e contrel stacks theICELCK for the given task, it attempts to restart all of the
components that have been freed by thecompletion of the operation. NEiWOBK INTERFACE CONTBOL fLOCK There is one Network Interface Centrol Elock (NICBLOK) for each defined 370% and
each resource attached to a3270 bisynchronous line. The NICELOK provides
the correspondence between the line or
device address and theFhysical resource
connected to that line. This block not
only defines the identityof the terminal type, line, or control unit but it also
contains flags and statusinformation pertaining to that resource. If the
defined resource is aremote 3270 component, the NICELOK ccntains the current
line coordinates
l polling and selection
characters information as veIl.
Theremainder of this secticn describes
the realI/O control blocks.
80IBM VM/370 Data Areas and Control Block Logic
returned
the
In addition, the
flags that indicate the current state of
the operation (such as, whether or not an
error has occurred, if an errcr recovery
condition returned fro. the
signals the end of the operation.
tlocks, they also contain forward and
backward queue
which the
In general, the
given operation progresses through the
system
until a path is at last free to the device.
A
is complete, the
the
on the queue are unstacked and control is
passed to the point
Interrupt Return Address
I/e contrel stacks the
components that have been freed by the
each resource attached to a
the correspondence between the line or
device address and the
connected to that line. This block not
only defines the identity
contains flags and status
defined resource is a
line coordinates
l polling and selection
characters information as veIl.
The
the real
80