A00

Explanation
During processing of an I/O request, execute channel
program (EXCP) encountered an error while an appendage was running.
Each X'A00' abend code has a reason code that shows which
appendage contained the error: Code
Explanation
1
Program controlled interrupt (PCI) appendage
2
Start I/O (SIO) appendage
3
End of extent (EOE) appendage
4
Channel end (CHE) normal end appendage
5
Abnormal end (ABE) appendage
6
Caller's page fix appendage

System action
The system abnormally ends the current task. The
system writes a logrec data set error record and issues a SNAP dump.

System programmer response
In the dump, look at field TCBEXCPD
at offset X'C0' in the task control block (TCB) for the current
task.  TCBEXCPD points to the EXCP debugging area (XDBA). The XDBA
contains diagnostic data associated with the EXCP processor. To determine
which appendage was active, see the microfiche mapping for data area
XFRR of the EXCP/EXFR FRR parameter area.
If the error recurs
and the program is not in error, look at the messages in the job log
for more information. Search problem reporting data bases for a fix
for the problem. If no fix exists, contact the IBM® Support Center. Provide the logrec data set
error record, the JCL for the job, and the SNAP dump.

Programmer response
If EXCP is being used for I/O operations,
this is an error in the appendage identified by the reason code. Fix
the appendage and run the job again. If the error persists, run the
job again requesting an ABEND dump and then notify the system programmer.

Source
Execute channel program (EXCP)