IBM System/360 System Programmer's Guide

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

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English