Special tag diagnostics

The special tag diagnostics feature captures and logs the internal processing of operations when the selected tags are sent to the OPC UA Server for monitoring and when values are written to or received from the server for those tags. Because these operations are saved in the event log, use this feature only with tags that change value slowly or on-demand.
Use special tag diagnostics when:
  • An unexpected or intermittent value is received.
    Add the tag whose value is not expected to change. If the value changes, the details will be captured on the
    FactoryTalk Diagnostic Log
     tab of FactoryTalk OPC UA Connector.
  • An expected value is not received.
    Add the tag whose value is expected to be received. If the value is received, the details will be added to the event log.
To identify when it should have been received, additional diagnostic information might be needed.
  • If the value is updated due to a manual event such as clicking a button, examine the
    FactoryTalk Diagnostic Log
     tab after the manual event occurs. If the log does not contain the expected information, something is preventing FactoryTalk OPC UA Connector from receiving the value.
  • If the value is updated due to intermittent events in the system, additional diagnostic data, such as tracing, can be used to correlate the other event in the system to the expected value that FactoryTalk OPC UA Connector receives. Correlating these two sources of data must be done manually.
    TIP:
    Use Wireshark to capture information sent between FactoryTalk OPC UA Connector and the associated OPC UA Server. If security is enabled, the connection must be configured for no security policy or limited to signing. Encrypting the communications might result in the detailed information being unreadable.
The following three system tags control and display special diagnostic information for selected tags:
Tag
Description
@Diagnostic Items\@DP_TagDetailsDisplay
Displays the last message when interactions with the tag occur rapidly. Only the last operation is visible.
  • Type:VT_BSTR
  • Access: Read-only
  • Resettable: Yes with the @DP_CounterResetCmd tag
See Displaying diagnostics tags for more information.
@Diagnostic Items\Retained\@DP_TagDetails
Enters or displays tags to be monitored for special diagnostics. This attribute accepts multiple tag references but requires each tag reference to be written individually. When a valid reference is accepted, it will be appended to the list of tags visible when this attribute is read. All settings are retained across restarts.
  • Type: VT_BSTR
  • Access: Read/Write
  • Resettable: No
See Adding or removing tags for more information.
@Diagnostic Items\Retained\@DP_TagDetails_LogToFTDiag
Logs messages to FactoryTalk Diagnostics optionally. Setting is retained across restarts.
  • Type: BOOL
  • Access: Read/Write
  • Resettable: No
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