Steps for analyzing session outages (server)

The preceding output is needed to begin diagnosis of a session outage reported against Telnet. It is also helpful to know what processing the Telnet user was doing at the time of the interrupted session.

Perform the following steps:

1. If a timeout due to inactivity or termination due to TIMEMARK processing is suspected, check the values set in the PROFILE data set.
2. Additional messages are issued for session outages when the Telnet DEBUG features are active. See z/OS Communications Server: IP Configuration Guide for details of the Telnet DEBUG features.
3. Check the documentation listed in Documentation for indications of an error.
   • If the MVS™ system console indicates a VTAM® error, continue diagnosis with your VTAM programmer.
   • If the console shows a Telnet or TCP/IP error, check z/OS Communications Server: IP Messages Volume 1 (EZA) or z/OS Communications Server: IP Messages Volume 4 (EZZ, SNM) and follow the directions for system programmer response for the message.

   If messages are found that do not lead to an accurate diagnosis and resolution of the error, search the APAR data base, available at for more information. If this does not provide a solution, contact the IBM® Software Support Center.

4. If only one Telnet user session was affected, continue with step 5. Otherwise, go to step 7.
5. If the problem can be re-created by performing the same operation or processing, run the following traces:
   • TCP/IP packet trace filtered using the IP address of the failing client
   • Component Trace output (CTRACE) specifying the Telnet option
   • VTAM Internal Trace (VIT)
   • VTAM buffer trace output with AMOUNT=FULL specified.
   Note: Contact your IBM Software Support Center for information about options needed before running these traces.
6. If all Telnet user sessions were interrupted, do one of the following:
   • Check the MVS system console and LOGREC for abends.
   • Check for loss of network connectivity. Verify whether all the TELNET users come in through the same channel interface or through a common router.
7. If there are no messages or abends and all Telnet user sessions have been disconnected, the traces listed in Step 5 are needed during a recurrence of the failure.
   A dump of the TCP/IP address space or a dump of the Telnet address space should be taken at this time. To capture the necessary areas of storage in the DUMP command, include:

   SDATA=(CSA,LSQA,PSA,RGN,SQA,SUM,SWA,TRT,LPA)

   Instructions on obtaining a dump can be found in z/OS MVS Diagnosis: Tools and Service Aids for your release of MVS.