Analysis

Use the following checklist to check for incorrect variable value:
  1. Is the object identifier in the MIB description file correct?
  2. Were any errors reported at the SNMP agent when the variable was requested?
  3. Is the variable being cached at the SNMP query stack?

    The SNMP query stack uses the hlq.MIBDESC.DATA data set to determine the length of time to cache the variable value (or a default time length if the variable is not found in the hlq.MIBDESC.DATA data set). If the variable is requested before the caching time is up, the cached value is used instead of obtaining a new value.

  4. Is the variable cached at the TCP/IP subagent?

    The TCP/IP subagent caches variable values for the length of time specified by the ibmMvsSubagentCacheTime MIB object, set by default to 30 seconds.

  5. Is the variable supported by the Network SLAPM2 subagent? If so, is it being cached? The Network SLAPM2 subagent caches MIB objects for 30 seconds by default, but the cache time can be overridden at subagent initialization time with the -t parameter.
  6. Is the variable cached at the TN3270E Telnet subagent? The TN3270E Telnet subagent caches variable values for the length of time specified by the CACHETIME keyword on the TNSACONFIG profile statement, set by default to 30 seconds.
If the problem still occurs after checking the preceding items and making any needed changes, obtain the following documentation:
  • SNMP agent level three showing what was returned to the client.
  • For the TCP/IP subagent, ITRACE level four trace output showing what the subagent returned to the SNMP agent.
  • For the OMPROUTE subagent, syslogd output obtained by starting OMPROUTE with the -s1 option or by issuing the MODIFY SADEBUG command to start OMPROUTE subagent tracing
  • For the Network SLAPM2 subagent, syslogd output obtained by the Network SLAPM2 subagent with the -d 131 option or the MODIFY DEBUG,LEVEL command to start Network SLAPM2 subagent tracing.
  • For user-written subagents, DPIdebug(2) output which is sent to the syslogd. For more information about reading the syslogd traces, see the z/OS Communications Server: IP Configuration Guide.
  • For the TN3270E Telnet subagent, syslogd output from the TNSATRACE keyword on the TNSACONFIG profile statement showing what the subagent returned to the SNMP agent.

In the traces, verify that the variable value is passed correctly from the SNMP subagent to the SNMP agent and from the SNMP agent to the client.

The following documentation might also be needed in some cases, but it is suggested that the IBM® Software Support Center be contacted before this documentation is obtained:
  • Dump of TCP/IP address space (for TCP/IP and TN3270E Telnet subagent variables).
  • Dump of SNMP query stack address space
  • Dump of OMPROUTE address space (for OMPROUTE subagent problems)
  • Dump of Network SLAPM2 subagent address space (for Network SLAPM2 subagent problems)
  • Incorrect values from the TCP/IP subagent are probably due to an error in the TCP/IP stack. In this case, a dump of the TCP/IP address space and a CTRACE from the stack might be useful. You can also use the Netstat command to verify that the TCP/IP subagent is reporting what the TCP/IP stack believes the value to be.

Information about obtaining a dump can be found in z/OS MVS Diagnosis: Tools and Service Aids. Obtaining SNMP traces is discussed in SNMP traces.

Parent topic: Variable value incorrect