I've remembered a little more about session hang and MTU size. 1500 is supposed to work everywhere, however there are some things in the past that just didn't work with 1500, and the symptom was that things just quietly hung. Some times it would even paint part of the screen and hang. Changing the client side MTU to something smaller, maybe 1400, would "fix it". It probably didn't fix it, it just masked whatever the bug was elsewhere.
Isn't token ring MTU something less than 1500? A few years ago, a Linux sysadmin was using dyndns to get back to his home system and it would hang in a similar manner. I had him set his MTU down a little and it started working. I think the problem ONLY happens when a message at MTU 1500 doesn't need fragmented, but at the lower MTU DOES need fragmented. Len Rugen University of Missouri Division of Information Technology Systems & Operations - Metrics & Automation Team ________________________________________ From: IBM Mainframe Discussion List [[email protected]] on behalf of Elardus Engelbrecht [[email protected]] Sent: Friday, May 06, 2016 2:14 PM To: [email protected] Subject: Re: zSECURE 32 x 80 Hang George Henke wrote: >Whenever we Dial into our z/OS VM with PCOMM and 32X80 screen size it hangs at >the very end of the ISPF dialog and after displaying the final ISPF dialog >screen. What do you mean by 'hang'? Are your sessions standing still, waiting for something requiring a cancel of your session? Is your Keyboard locked (Host keyboard lock status)? Is this only you [1] or are others also affected? What is the name (PANELID) of those dialog screens? Perhaps those panels and or the driving dialogs were coded incorrectly? Or should I ask, what were you actually doing from one panel to the other? I see ZSECURE in Subject. Are you referring to IBM's security tool product? If so, open a PMR. If IBM can recreate your problem this should be very interesting. >24 X 80 is ok. >Coming through PCOMM on CITRIX is ok. >Coming through a NATed address in PCOMM is also ok. With what screen size for above? Now you're talking about NATed address, check your firewall settings on your workstation and on all parts of your network. >It only fails when we Dial In with 32 X 80. If you're in office, can you use 32x80? I always use 32x80 from home and from office. I hate 24*80, but then it is just me... ;-) >Any ideas? Probably a bad logmode in VTAM / TCP/IP? Do you use Extended Attribute? What about larger sizes? Can you use them? Len Rugen said something about MTU. Hmmm, very interesting. Perhaps you can review your PCOMM settings? Oh, with what version of PCOMM and z/VM are you working? Can you extract a session trace from your PCOMM session and see if some invalid characters were transmitted? Sorry for asking so many bothersome questions, but I have done similar, but weird session+communication debugging ages ago... Groete / Greetings Elardus Engelbrecht [1] - Check your profile dataset and your ISPF screen attributes and settings. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
