Hmmm.. almost sounds like QWS3270 may be getting impatient when waiting for a reply. That is, the 'keep alive' time may apply only to an idle session as opposed to a wait for reply situation.
I'd look into QWS3270 parameters. -----Original Message----- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Thompson, Steve Sent: Thursday, June 18, 2009 9:29 AM To: IBM-MAIN@bama.ua.edu Subject: TCP Settings for KeepAlive I've run into a problem where I have TN3270 sessions attached to a VTAM session manager. The problem is this: When the system, where the VTAM session manager is running, is at 100% for extended periods (5 minutes or more), AND, you have a TSO session on the system where the session manager is, AND that TSO session attempts to run a "long running task" (Endevor update to promote source is an example), the TSO session will continue to run, BUT the TN3270 session will be timed-out and dropped. In this case the TN3270 is QWS3270 Plus. In tracing this, we see that QWS is "posted" with a lost connection. However, QWS is running the TCP keep alive at about a 5 minute interval. And the last thing that QWS shows is it sent a buffer to the host and is now waiting for a response when it gets this lost connection posting. I have been looking at the z/OS Comm Server manuals (even searching them) and I don't see anything that needs to be changed in the configuration. I have looked at various APARs (particularly the ones about IMS and additional keepalive support from 1.7 and later). But I don't see anything that seems to apply. The other thing about this that is interesting, those running Hummingbird don't seem to have this drop problem. And this is something that I can recreate at will. Note: TSO is not timing out. This is specifically a TCP connection termination issue that is timing related. It takes the z/OS system (1.8) going to 100% busy for 5 minutes or longer. And, while this is happening, I can be directly connected to other MVS or VM systems and they are not affected. So anyone have any idea where I need to look in the config parms for TCP (or VTAM?). Regards, Steve Thompson NOTICE: This electronic mail message and any files transmitted with it are intended exclusively for the individual or entity to which it is addressed. The message, together with any attachment, may contain confidential and/or privileged information. Any unauthorized review, use, printing, saving, copying, disclosure or distribution is strictly prohibited. If you have received this message in error, please immediately advise the sender by reply email and delete all copies. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
