Explanation
This message is the first of a group of unsolicited
messages that VTAM® issues when
the TDUDIAG threshold is reached for a TG. The TDUDIAG threshold is
a numeric value specified on the TDUDIAG start option. If you receive
this message, it might be an indication of a TDU war, which is an
endless exchange of TDUs in contention over the same topology resource,
resulting in continuous performance degradation of the APPN network.
Three
counters are monitored to determine when the threshold is reached
for a TG:
- A count of the number of times that the host network node updates
the resource sequence number (RSN) for the TG.
- A count of TDUs that are received and accepted for the TG. A TDU
is accepted when it contains new information about the TG, and the
topology database is updated with the new information.
- A count of TDUs that are received and rejected for the TG. A
TDU is rejected when it contains outdated information about the TG.
A new TDU is built from the local topology database and is sent to
correct the information.
When the TG identified in this message reaches the threshold
value, TDU diagnostic information is appended to the TG record in
the topology database. This action occurs every time the RSN is updated
by the host network node or when a TDU that contains TDU diagnostic
information is received for that TG.
See the TDUDIAG
start option information in z/OS Communications Server: SNA Resource Definition
Reference.
A complete description of the
message group follows the example.
IST2299I TDUDIAG THRESHOLD REACHED FOR TG: TGN = tg_num
IST2256I ORIG = origin_node - DEST = dest_node
IST314I END
IST2299I - This message identifies the TG number of the TG that reached
the TDUDIAG threshold.
- The tg_num value is the TG number of the TG
that reached the TDUDIAG threshold.
IST2256I - This message identifies the origin and destination of the TG
that reached the TDUDIAG threshold.
- The origin_node value is the network-qualified
CP name of the origin node of the TG that reached the TDUDIAG threshold.
- The dest_node value is the network-qualified
CP name of the destination node of the TG that reached the TDUDIAG
threshold.
System action
Operator response
To determine whether this TG might be a topology
resource that is in contention in a TDU war, use the information
about display TDU information in z/OS Communications Server: SNA Diagnosis Vol
1, Techniques and Procedures and do the following:
- Issue the DISPLAY NET,TOPO,LIST=TDUINFO,SCOPE=ACTIVITY command
to determine whether the TG is one of the topology resources with
the most frequent TDU activity.
- Repeat the display several times to determine whether there is
a pattern of excessive TDU activity for the TG.
- Issue the DISPLAY NET,TOPO,LIST=TDUINFO,SCOPE=RECENT command to
determine whether the TG is one of the topology resources with the
most recent TDU activity.
- If the previous displays indicate excessive TDU activity for the
TG, the following displays might provide information about the network
nodes that are causing the performance degradation (TDU war):
- The DISPLAY NET,TOPO,LIST=TDUDIAG command provides a summary of
nodes and TGs with saved TDU diagnostic information.
- The DISPLAY NET,TOPO,LIST=TDUDIAG,ORIG=origin_node,DEST=dest_node,TGN=tg_num command
provides details about saved TDU diagnostic information for the TG.
- If you can identify the network nodes that are involved in the
TDU war, end the CP-CP sessions between one of the network nodes
involved and all other network nodes in the network or subnetwork.
- If you cannot stop the TDU war, save the system log and request
a dump for problem determination. Contact the system programmer.
Tip: On the DISPLAY TOPO,LIST=TDUINFO and DISPLAY
TOPO,LIST=TDUDIAG summary command output, a RSN value of ********
or TDU counter values of ***** indicates the value is greater than
the available space for the value to be displayed in messages IST1778I
or IST2293I. You can clear the TDU counters, but not the RSN, with
the CLEAR=YES operand specified on either the DISPLAY TOPO,LIST=TDUINFO
command or the DISPLAY TOPO,LIST=TDUDIAG summary command. Alternately,
you can enter the command with the FORMAT=LONG operand to display
these values in a format that includes two lines of output for each
resource.
System programmer response
Take the following actions:
- If the operator provides output from the DISPLAY TOPO,LIST=TDUINFO
or DISPLAY TOPO,LIST=TDUDIAG, use the information about display TDU information in z/OS Communications Server: SNA Diagnosis Vol
1, Techniques and Procedures to analyze the TDU activity. If possible,
identify the topology resource that is in contention and the network
nodes that are involved in the TDU war.
- If you have access to IBMLink, search for known problems in this
area. If no applicable matches are found, report the problem to IBM® by using the Electronic Technical
Report (ETR) option on IBMLink.
- If you do not have access to IBMLink, report the problem to the IBM software support center.
User response
Problem determination
See the system programmer response.
Source
z/OS® Communications
Server SNA
Module
Routing code
Descriptor code
Automation
If the TDUDIAG start option is set to the default
value 1000 or higher, this message might be an indication of a TDU
war and automation is suggested.
Example
IST2299I TDUDIAG THRESHOLD REACHED FOR TG: TGN = 21
IST2256I ORIG = NETA.CPS05 - DEST = NETA.CPS10
IST314I END