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channel
programs have been completed.
You specify, in the input/output
block, whether the channel prograw is related to others.
If a permanent error occurs in a channel program that is
related
to
other
requests,
the
request
elements
for
all
the
related channel
programs are removed from their queue and made available.
This
process
is
called
purging.
The
addresses of the input/output blocks for the
related channel programs are chained together, with the address
of
the
first
input/output
block
in the chain placed into the "User Purge lOB
Address" field of the data extent block.
The
address
of
the
second
input/output
block
is
placed
into the "Restart Address" field of the
first input/output block, and so on.
The last input/output block in the
chain is indicated by all ones in its Restart Address field.
The
chain
defines
the order in which the request elements for the related channel
programs are removed from the request queue.
For all requests that are related to the channel
program
in
error,
the
system
places completion codes into the event control blocks.
The
IFLGS field of the data control block is also flagged.
Any requests for
a data control block
with
Error
flags
are
posted
complete
without
execution.
If
you
wish
to
reissue requests that are related to the
channel program in error, you rrust reset the first two bits of the IFLGS
field of the data control block to zeros.
You
then
issue
a
RESTORE
macro-instruction, specifying, as the only parameter, the address of the
"User
Purge
lOB
Address" field of the data extent block.
This causes
execution of all the related
channel
programs.
(The
RBSTORE
macro-
definition and how to add it to the wacro-library are in the Appendix of
this
chapter.)
Alternatively,
if you wish to restart only particular
channel programs rather than all of
them,
you
may
reissue
the
EXCP
macro-instruction for each channel program desired.
APPENDAGES
This
section
discusses
the appendages that you may optionally code
when using the
EXCP
macro-instruction.
Before
a
programmer-written
appendage
can
be
executed,
it
must
be included in the SVC library.
These procedures are
explained
first;
descriptions
of
the
routines
themselves and of their coding specifications follow.
DEFINING APPENDAGES
An
appendage must be defined in a DD statement as a member of a SYSl
partitioned data set.
The full member narre of
an
appendage
is
eight
bytes
in
length, but the first six bytes are required by IBM standards
to be the characters IGG019.
The last two characters must
be
provided
by
you
as an identification; they may range in collating sequence from
WA to Z9.
ENTERING APPENDAGES INTO SVC LIBRARY
The SVC library is a partitioned data set named SYS1.SVCLIB.
You can
insert an appendage into the SVC library during
the
system
generation
process.
In
either
case, the routine rr.ust te a member of a cataloged
partitioned data set whose name begins with SYS1.
To enter a routine into the SVC library during system generation, you
use the SVCLIB macro-instruction.
The format of this
macro-instruction
is
given
in
the
publication
IBM System/360 Operating System: System
Generation, Form C28-6554.
80
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