Re: Cleanup after program failure

>Date: Wed, 02 May 2001 22:51:31 +1000
>From: Matthias Oertli <oertlim@s054.aone.net.au>
>
>The difficulty is that program B needs a different environment to
>program A: A slight change in the library list and a modified data
>area.
> ...
>My problem is this: If program B (or the CL) fails for whatever
>reason, program A regains control without the environment having been
>restored to what it should be which could mean disaster.
>
>How can I guard against this situation?

Matthias, the safest way to ensure that cleanup is always done
is to use an ILE cancel handler which will fire if your program crashes
or if it gets canceled (sys-req 2 etc).  I find it easiest to put
the cleanup code in a procedure, and then call the cleanup procedure at
the normal end of the routine, and also call the cleanup procedure
from the cancel handler.  There's an RPG example of enabling and coding
a cancel handler in the ILE RPG Programmer's Guide, here:
http://publib.boulder.ibm.com:80/cgi-bin/bookmgr/BOOKS/QB3AGY03/3.2.5

If you're not using ILE, change program B to be an ILE program and
have it handle the library list stuff and enable the cancel handler,
and then call the existing program B, renamed to B2.

Others have recommended condition handlers, but they don't handle
cancellation due to sys-req-2 or due to using F3 from the debugger,
while cancel handlers handle any abnormal termination, due either
to a crash or to a cancellation.

Handling the cleanup in the caller is also an option, but it's not
always the best solution, especially if the program is called from
several different callers.  In my opinion, cleanup should be handled
by a program, not by its callers.

(Sorry for the late response - I've been on holiday.  Wheee!)

Barbara Morris


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