Re: STRDBG/ENDDBG required to prevent Java open exception -- MIDRANGE-L



Scott Klement wrote:

I suspect that there's a class that's trying to write data to the stderror stdout data stream, and it just assumes that it'll be available foruse. When it's not available, it crashes.

I sort of thought that too, so I modified Barbara's program to open themto actual stream files in /home instead of /dev/null. But there wasnothing in them after the program closed them.

On a Unix system the open would affect the current process. Any newprocesses would typically inherit the current processes open descriptors,so they'd be affected too. Normally when you call a program on a Unixsystem, you'll create a new process, run the program in the new process,and wait for it to complete. This creates something very similar to the"call stack" we have on i5/OS, allowing you to kill the called programsindividually, handle their errors, etc. If the caller doesn't want towait for the called program to complete, it doesn't have to, this allowsmultiple programs to run concurrently (much like submitting to batch oniSeries).
Anyway... the gist of it is that closing these descriptors would notaffect your caller, it'd only affect processes that you create. Typicallyyou'd close FD's 0-2 and open them pointing to /dev/null so that newprocesses would no longer have a connection to the terminal. This isuseful when running what we think of as a "batch job" that doesn't have aconnection to a terminal.
On iSeries, I don't know exactly how this works. Would it be scoped tothe job, considering the job to be equivalent to a process? That'd makethe most sense, but I don't know for sure. If it's scoped to the job,closing them could have repercussions on programs called later. Youwouldn't have these problems on a Unix system unless your program thatclosed the FDs was called in the same process as the caller, which isn'tthe normal paradigm.

Do Unix programs typically expect their caller to have already openedthe std io files?

There are 5 threads in JAVW status after my program has opened thespreadsheet. It's unclear to me how those threads relate to my program.Are they part of my program's call stack entry?
I suspect that they're part of the JVM, not your program.

So the JVM is created in my job's memory, but as independent threadsthat communicate by

pipes, semaphores, shared memory, common files, something else?

*Peter Dow* /
Dow Software Services, Inc.
909 793-9050
pdow@xxxxxxxxxxxxxxx <mailto:pdow@xxxxxxxxxxxxxxx> /