Back a few years I wrote and taught a CP and CMS Debugging Workshop. The course taught dump reading and real time debugging. We used CP DUMPs that had PTFs associated with them. Prior to reading the DUMP information was conveyed concerning interrupt handling, registers, control blocks, major CP subsystems, etc. Then the diagnostic clue seeking began. So it was a combination of CP internals and problem solving.
In addition to the aforementioned skills a lot of focus was required. I had no problem giving answers but I expected that attendees could at least run chains, find save areas, identify key control blocks and otherwise goal seek throughout a DUMP. Every VM SYSPROG should go through some internals training and a bit of DUMP reading. Alas the industry doesn't demand it but it should. Raise their VM consciousness. It isn't just a layer to run Linux machines. Dvaid Kreuter -------- Original Message -------- Subject: Re: 3 job openings for mainframe Assembler/C programmers, dump readers From: Rob van der Heij <[email protected]> Date: Fri, July 26, 2013 2:02 am To: [email protected] On 26 July 2013 00:44, Bernd Oppolzer <[email protected]> wrote: > Of course you can teach dump reading and debugging; > Steve Comstock does it, I do it, and others do it as well. > At least it gets them beyond the point where they claim it got a protection exception on a LR instruction ;-) I think both MVS and VM use similar linkage conventions (unlike zLinux) so you can walk back the subroutine nesting and understand where you are in there (don't think anyone destroys save area on exit, so you can be tricked in walking it the wrong direction). But experience makes a big difference. That's why you spot odd patterns, recognize a page table in memory, have your own macros to find stuff, or even recognize the program check old PSW from an ancient release. We used to have a set of dumps around for new sysprogs to practice. When you get into this, it's nice to start with problems that can be resolved so you don't get away with "there is nothing useful in the dump" claims. But it may still not be anyone's job to sit down with a dump for a few hours and come up with the exact scenario to reproduce and fix the problem. Rob
