There may be a number of reasons why SNMP Client Driver is unable to update the value of a data point tag. For example:
When there is an error, the SNMP Client Driver writes values to the TagErrorCode and DataSourceError properties to explain why.
The TagErrorCode field provides the primary reason why a tag is not updating:
| TagErrorCode | Description |
|---|---|
| 0 | No error. |
| 1 | The IODataSource property is not valid. |
| 5 | The data returned by the SNMP Agent could not be converted to the type required by the tag. |
| 6 | The IOItemName property is not a valid ASN1 object identifier. |
| 20 | The SNMP Agent responded with a PDU status error. The DataSourceError will contain the PDU status error code. |
| 21 | The reply from the SNMP Agent does not contain a variable binding list (VarBindList). |
| 22 | The reply from the SNMP Agent did not contain a value for this tag. |
| 23 | The SNMP Agent responded with a VarBind exception. The DataSourceError will contain the exception number. |
| 24 | The driver does not support the SNMP Data Type returned by the SNMP Agent. The DataSourceError will contain the data type that is not supported. |
| 25 | The SNMP Agent is offline. |
| 26 | Invalid username. The SNMP agent did not recognize the user configured in the V3UserName property. |
| 27 | Authentication error. The V3AuthPassword value is incorrect. |
| 28 | Response too big. The response was too large for the SNMP Agent. Consider decreasing GetRequestMaxObjects. |
| 29 | No such name. No such item exists in the SNMP Agent. |
For certain TagErrorCode values, the DataSourceError field provides additional information.
For an overview of the SNMP Client Driver.
For the meaning of terms used in Fernhill SCADA.