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Documentation Index

Fetch the complete documentation index at: https://docs.cognite.com/llms.txt

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We recommend accessing the server through the UAExpert tool.
This assumes that you have first run the configuration tool as described in the configuration settings.

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Unable to connect to the server

If the extractor isn’t able to connect to the OPC UA server, try these solutions.
If you get the error message Unable to connect to discovery server, make sure that you have specified the correct endpoint-url in the configuration file and that it’s possible to connect to the server from where the extractor is running.Also, try connecting with UAExpert to verify that you can connect to the server.
If you get the error message Identity token rejected when starting the extractor, verify that you have specified the correct username/password.
If you get the error message Identity token rejected when starting the extractor, try setting source.auto-accept to true to resolve the issue.OPC UA uses a system of server/client certificates. This error message means that the server doesn’t trust the client certificate. The server software typically has a system to accept incoming connections, but the system is application specific.Similar errors are also produced if the extractor rejects the server.
This typically occurs if the server can’t handle a high load. Try to inspect what the extractor was doing as it crashed, then reduce source/browse-nodes-chunk, source/browse-chunk, source/attributes-chunk, or source/subscription-chunk in the configuration file.Alternatively, increase source/keep-alive-interval.
This is an issue with the server certificate unless a custom client certificate is being used.By default, SHA1 server certificates are considered insecure. As a workaround, you can set <RejectSHA1SignedCertificates>false</RejectSHA1SignedCertificates> under SecurityConfiguration in opc.ua.extractor.Config.xml.You can also set source.ignore-certificate-issues to true.
This is an issue with the server certificate unless a custom client certificate is being used.Either increase the key length of the server certificate or adjust MinimumCertificateKeySize under SecurityConfiguration in opc.ua.extractor.Config.xml.You can also set source.ignore-certificate-issues to true.
This is an issue with the server certificate unless a custom client certificate is being used.The server certificate lacks the data-encipherment usage flag. This is required by the OPC UA standard.As a workaround, you can set source.ignore-certificate-issues to true.

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Bad or missing data

If the extractor isn’t able to retrieve all data or receives data in the wrong format from the OPC UA server, try these solutions.
First, make sure that the server has variables that can be mapped to time series. In UAExpert, these show up as green labels.Next, try to set extraction/data-types/allow-string-variables to true. This may cause time series you would rather have as numeric to appear as string. See Time series are string-valued but should be numerical.If the time series are still missing, the issue is most likely related to their dimensions. By default, the extractor requires that variables are either Scalar or OneDimensional. If you have arrays in your server, they must be fixed size and define the ArrayDimensions attribute. Try setting extraction/data-types/unknown-as-scalar to true. This will help if the variables have ValueRank equal to Any or OneOrMoreDimensions, in which case they will be treated as scalar.If variables still doesn’t appear, check to make sure you haven’t filtered them out in any way.
This is generally a question of their OPC UA data type. The extractor tries to guess which mapping makes the most sense but doesn’t always succeed.First, try setting extraction/data-types/auto-identify-types to true.Next, try setting extraction/data-types/null-as-numeric to true. This will treat variables with null DataType as numeric variables. Do this only if you are sure none of these should be string values. If this is the case, either filter these out or contact the server administrator. Unknown data types aren’t supported by the extractor, except with this workaround.You can find the data type in UAExpert on the right side after selecting a variable.
Variables in OPC UA are mapped to time series, while properties are mapped to metadata. Sometimes the server will have variables that represent metadata. To map these over, you can use extraction/transformations to select the nodes you want as metadata.
Last modified on January 27, 2026