Steps for analyzing logon problems (server)

Determine why clients are unable to connect to a host application.

About this task

Table 1 shows symptoms of login problems and refers to the steps needed for initial diagnosis of the error. The information following the chart and associated information can be used for extended diagnosis, if the problem persists.

Table 1. Telnet login problems
Login problem Analysis steps
No LUs available 1, 2, 6, 10, 13
OPEN failure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
x-clock (Telnet solicitor panel) 1, 2, 3, 4, 5, 6, 7, 10
x-clock (blank screen) 1, 2, 3, 6, 7, 8, 10, 12
x-clock (application panel) 7, 8, 10
Incorrect USSMSG or DEFAULTAPPL 3, 4, 5, 6, 1, 13, 14

Procedure

Perform the following steps:

  1. Have VTAM® APPL definition statements been coded correctly?
    Note: There must be a VTAM definition statement or model application name for each LU coded in the PROFILE data set.
  2. Is the VTAM node containing the Telnet LU definitions active?
  3. Is there a DEFAULTAPPL coded in the PROFILE data set?
  4. Is the host application (or DEFAULTAPPL) active?
  5. Is there an ALLOWAPPL statement coded that includes the requested application?
  6. Have comment delimiters been added or removed as needed in the BEGINVTAM section of the PROFILE data set?
  7. Have correct LOGMODEs (or required overrides for SNA) been coded in the PROFILE data set?
  8. Does the host application have BIND (session parameter) requirements that are not met by the specified LOGMODE?
  9. Is the MSG07 parameter coded in the PROFILE.TCP data set?
    Note: MSG07 returns information to the end user indicating the reason for the failure.
  10. Are any abends (in VTAM, host application, or TCP/IP) indicated on the MVS™ system console?
    Note: If an abend occurred, see the section on abends to continue investigation of the problem.
  11. Check the PROFILE data set for the IP to LU mapping.
  12. Is an SSL client attempting to connect to a basic port or is a basic client trying to connect to an SSL port?
  13. Use the D TCPIP,,T,PROFILE,DETAIL command to view the active profile definitions.
  14. Determine whether USSTCP within the TCPIP PROFILE points at the correct USSTAB, because this could also cause an incorrect USSMSG to be displayed.

Results

If the problem still occurs after following the preceding procedure and making any needed changes, obtain the following documentation:
  • TELNET display of the LUNAME or CONN ID of affected client, for example, D TCPIP,,T,CONN,LUN=luname.
  • VTAM DISPLAY of Telnet LU.
  • VTAM DISPLAY of the target host application.
  • Activate DEBUG DETAIL and review additional diagnostic information this function provides.
For information about the Telnet Display command options, see the z/OS Communications Server: IP System Administrator's Commands.
The following documentation might also be needed in some cases, but it is suggested that your IBM® Software Support Center be contacted before this documentation is obtained:
  • TCP/IP packet trace and CTRACE with TELNET option filtered on the IP address of the failing client.
  • VTAM buffer trace of the Telnet LU.
  • VTAM INTERNAL TRACE (VIT) with options (API,PIU,MSG,PSS,NRM,SSCP).
  • Dump of the Telnet address space. To capture the necessary areas of storage in the DUMP command, include: 
    SDATA=(CSA,LSQA,PSA,RGN,SQA,SUM,SWA,TRT,LPA)

For information about obtaining VTAM traces, see z/OS Communications Server: SNA Operation or to z/OS Communications Server: SNA Diagnosis Vol 2, FFST Dumps and the VIT for your release. Instructions on obtaining a dump can be found in z/OS MVS Diagnosis: Tools and Service Aids for your release of MVS.

Parent topic: Logon problems (server)