12C

Explanation
During processing of a CHAP macro, the system found
an incorrect address for the task control block (TCB) for the subtask
whose priority was to be changed. The second operand of a CHAP macro
points to a fullword that contains the TCB address.
The address
was incorrect for one of the following reasons: It was not a valid TCB address.
The valid TCB at the address was not associated with a subtask
of the task issuing the macro.
It was not a multiple of 4.
The valid task has abnormally ended.

System action
The system abnormally ends the program that issued
the CHAP macro.

System programmer response
  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 source program listing for the job.

Programmer response
Change the address specification.  Ensure
that it and the TCB were not incorrectly modified by the problem program.
Correct the error.  Run the job again.

Source
Task management