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If you use the return address in register 14 to return control to the
system, the abnormal end appendage is entered.
An
end-of-extent
error
code
is
placed
in
the "ECB code" field of the input/output block for
subsequent posting in the event control block.
You may use the following optional return addresses:
• Contents of register 14 plus 4
The
channel
program
is
posted
complete, and its request element is made available.
• contents of register 14 plus 8 - The request is tried again.
You
may
use
registers
10 through 12 in an end-of-extent appendage
without saving and restoring their contents.
Note:
If an
end-of-cylinder
or
file-protect
condition
occurs,
the
input/output
supervisor
updates
the
seek
address to the next higher
cylinder or track address,
a~d
re-executes the request.
If the new seek
address is within the data
s~t's
extent, the request is executed; if the
new seek address is not within the data set's extent, the
end-of-extent
appendage is entered.
If
a
file
protect
condition
occurs and was caused by a full seek
(command code=07) imbedded within a
channel
program,
the
request
is
flagged as a permanent error, and the abnormal end appendage is entered.
'~
Channel End Appendage
This
appendage
is entered when a channel end, channel end with unit
exception, or channel end with wrong length
record
occur
without
any
other abnormal end conditions.
If you use the return address in register 14 to return control to the
system,
the channel program is posted complete, and its request element
is made available.
In the
case
of
unit
exception
or
wrong
length
record,
the
error
recovery
procedure is perforrred before the channel
prograrr is posted complete.
You may use the following optional return addresses:
• Contents of register 14 flus 4 - The channel program is
not
posted
complete, but its request element is made available.
• Contents
of
register 14 plus 8 - The channel program is not posted
complete, and its request element is
placed
back
on
the
request
queue
so that the request can be retried.
For correct re-execution
of the channel program, you must re-initialize
the
"Flags
1"
and
"Flags
2"
fields
of
the
input/output
tlock
and set the "Error
Counts" field to zero.
• Contents of register 14 plus 12 - The channel program is not
posted
complete,
and
its
request
elerrent
is
not made available.
(The
request element is assumed to be used in a
subsequent
asynchronous
exit routine.)
You
may
use
registers
10
through
13
in a channel end appendage
without saving and restoring their ccntents.
Abnormal End Appendage
This appendage is entered when a unit check, channel chaining
check,
program
check,
or
protection
check
is
detected
with normal ending
conditions.
In the case of error conditions that can be retried by
the
system's error routines, the appendage is entered a second time when the
input/output supervisor deterrrines that the error is permanent.
Execute Channel Program (EXCP) Macro-Instruction
83
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