TDUDIAG start option


                      (1)                   
   .-TDUDIAG--=--1000-------------------.   
>>-+------------------------------------+----------------------><
   '-TDUDIAG--=--+-resource_threshold-+-'   
                 +-ALWAYS-------------+     
                 '-NEVER--------------'

Notes:

TDUDIAG is meaningful only if the NODETYPE=NN start option is also being used.

dependencies:

applies only to APPN topology resources

range:

1 - 65535

Specifies when TDU diagnostic information is included with node or TG control vectors in a topology database update (TDU). This diagnostic information provides the CP name of the network node that updated the resource sequence number (RSN) for a topology resource, which helps determine which network nodes are causing a TDU war. A TDU war is an endless exchange of TDUs in contention over the same topology resource, which results in continuous performance degradation of the APPN network.

TDUDIAG=resource_threshold: Specifies a threshold number of times that this network updates the RSN for a node or TG topology resource within a 24–hour period. When this threshold is reached, TDU diagnostic information is appended with the topology control vectors that are included in a TDU for that resource every time the RSN is updated by this node.
Tip: The number of RSN updates for a topology resource involved in a TDU war increases rapidly and can reach a very high value before the problem is detected. A low TDUDIAG threshold is not necessary to capture the information that you need to diagnose the TDU war.
TDUDIAG=ALWAYS: Specifies that TDU diagnostic information is always appended with the topology control vectors that are included in a TDU for a topology resource when the RSN for that resource is updated by this network node.
Result: TDU diagnostic information that is received and sent in TDUs is saved with the node or TG resource in the topology database. Each topology resource can contain up to 50 of the most recent RSN update records, which can result in a significant storage increase if TDUDIAG=ALWAYS is specified. You can clear these RSN update records with the DISPLAY TOPO,LIST=TDUINFO or DISPLAY TOPO,LIST=TDUDIAG commands with the CLEAR operand specified. See the DISPLAY TOPO command in z/OS Communications Server: SNA Operation for additional information.
TDUDIAG=NEVER: Specifies that TDU diagnostic information is never appended with the topology control vectors included in a TDU.
Result: Not every network node in the network is required to append TDU diagnostic information in TDUs. However, because you cannot anticipate which network nodes are updating the RSNs of the resources that are in contention during a TDU war, you might not be able to diagnose the problem if one of the network nodes involved has TDUDIAG=NEVER specified or does not have support for TDU diagnostic information in TDUs.

Guideline: If you use the default value 1000 for the TDUDIAG operand, TDU diagnostic information is not added in a TDU for a resource unless a large number of RSN updates are occurring. A large number of updates might indicate a TDU war. Unless you have a compelling reason to change this value, you should use the default value for the TDUDIAG operand.

You can change the value of TDUDIAG by issuing the MODIFY VTAMOPTS command while VTAM® is running.