Why is my MPE job suddenly failing?

Why is my Job Suddenly Failing?

I had a recent call in to support asking why all of a sudden some jobs started failing in a job stream. The report was a blank line after run of a program suddenly started giving the error:

Missing colon before command name. (CIERR 981)

In previous incarnations the job stream with the blank line would NOT fail but nothing changed... of course. :)

First off I want to confirm that a blank line does abort a job stream.

	
	:comment bland line is next

	Missing colon before command name. (CIERR 981)
	REMAINDER OF JOB FLUSHED.
	CPU sec. = 1.  elapsed min. = 1.  THU, FEB  4, 2010, 10:47 AM.

And I found it does.

The customer though showed that the blank line was after
the run of a program and in this case I am using query as 
an example. We didn't see the same behaviour. Odd.
	:comment
	:comment test blank line after run query.pub.sys
	:comment
	:purge file1x
	:query


	HP32216N.03.18  QUERY/NM  THU, FEB  4, 2010, 10:18 AM
	COPYRIGHT HEWLETT-PACKARD CO. 1976

	exit


	END OF PROGRAM
	:showjcw jcw
	JCW = 0
	:showjcw cierror
	CIERROR = 0
	:eoj
	CPU sec. = 2.  elapsed min. = 1.  THU, FEB  4, 2010, 10:18 AM.


Some investigation and some clues from something I had remembered
investigating in 2001 allowed me to duplicate by switching to query
being run/resolved via a command file. 

In the above example even though the commands
were the same, query was being run via path resolution. This is the
part that was tricky and I later make the examples explicit by specifically
running query.pub.sys or using my query command file:

	
	:comment
	:comment  Blank line after query which resolves to a command file
	:comment
	:query


	HP32216N.03.18  QUERY/NM  THU, FEB  4, 2010, 10:20 AM
	COPYRIGHT HEWLETT-PACKARD CO. 1976

	exit


	END OF PROGRAM

	Missing colon before command name. (CIERR 981)
	REMAINDER OF JOB FLUSHED.


Another example but this time with garbage commands:

	
	:comment query command file with garbage after exit
	:query


	HP32216N.03.18  QUERY/NM  THU, FEB  4, 2010, 10:44 AM
	COPYRIGHT HEWLETT-PACKARD CO. 1976

	exit


	END OF PROGRAM
	yabba dabba doo
	Missing colon before command name. (CIERR 981)
	REMAINDER OF JOB FLUSHED.
	CPU sec. = 2.  elapsed min. = 1.  THU, FEB  4, 2010, 10:44 AM.


Now I switched back to running directly with the yabba dabba doo
still in the job and some other lines:

	:comment
	:run query.pub.sys


	HP32216N.03.18  QUERY/NM  THU, FEB  4, 2010, 10:45 AM
	COPYRIGHT HEWLETT-PACKARD CO. 1976

	exit


	END OF PROGRAM
	:showjcw jcw
	JCW = 0
	:showjcw cierror
	CIERROR = 383
	:eoj
	CPU sec. = 2.  elapsed min. = 1.  THU, FEB  4, 2010, 10:45 AM.
	

In the case of a run of the program file the garbage lines after the run
are being read as $stdin until it sees a "!". So what happens is the program
exits and the extra lines left in the stdin are thrown away.

However, if you switch this run to a command file, suddenly the job stops
running to completion.

So, if you have a customer that switches from say

query

which is run thru HPPATH resolution, to having 

query

be resolved via a command file, the jobs with blank lines or garbage after
the exit line will suddenly stop failing.

It's a bit tricky to diagnose especially if the customer doesn't believe you
or points to something else. I have not tested UDC's but I would believe that
they would have the same behaviour. My guess is that when a command file ends
MPE just reads the next line in the job stream, but when a program ends the
job stream is trying to re-orient itself in regard to stdin and just reads
until is sees a "!". That is the behaviour that I am seeing.

Any past labbies or gurus care to comment or have thoughts.