Problems with data returned by OPC server

The Unpack2 error messages in the local PI Message Log can indicate invalid data. In some cases, PI Interface for OPC DA might be sending data to Data Archive and also logging Unpack2 errors for the PI point, because the OPC server sends good values when it can and error codes when it cannot. Intermittent failures between the OPC server and the data source result in a combination of errors and values.

The following generic error messages are commonly logged:

In UnPack2 Tag MyPV.pv returns error 80020005: 80020005(Type mismatch)

In UnPack2 Tag MyPV2.pv returns error: The operation failed (80004005)

The following error messages indicate that the data received from the OPC server contained errors and the OPC server did not return a text explanation of the error:

In UnPack2 Tag MyPV3.pv returns error : Unknown error(800482d2)

In UnPack2 Tag MyPV4.pv returns error E004823E: Unknown error (e004823e)

In UnPack2 Tag MyPV5.pv returns error E241205C: Unknown error (e241205c)

In UnPack2 Tag MyPV6.pv returns error E2412029: Unknown error (e2412029)

To troubleshoot such data-related issues, consider the following causes and solutions:

• If you see Unknown errors, check with the OPC server vendor and have them look up the error code displayed in the error message. OPC servers can generate vendor-specific error codes, and only the OPC server vendor can explain what they mean.

• Restarting the OPC server might resolve the issue.

• Type mismatch errors indicate incompatible data types. Check for a mismatch between the Data Archive data type and the OPC item type. Check location2 settings. To avoid cache issues after data types are changed, restart the interface.

• Verify that the data type of the PI point can accommodate the range of values being sent by the OPC server. For example, if a PI point is defined as a two-byte integer and the OPC server sends values that are too large for it to accommodate, the point overflows.

• Make sure the data type of the OPC item and PI point are compatible.

• The data source might be sending corrupt data to the OPC server. Check for network issues that might corrupt the data packets.

• Check the size of the OPC server group. If the scan class contains more points than permitted in the OPC server group, Unpack2 errors might result. Consult the OPC server documentation for group size limits.

• If the point is digital, and the data can be read into a string PI point, and the underlying control system is Honeywell, the digital state strings in Data Archive might need to exactly match the string reported by the DCS. To determine the digital states, go to Honeywell Universal Station or GUS to look at each controller block (data source).