com.microsoft.dataflow.broker.InvalidOperationException: Only one valid authentication should be used for linkedservice

@Kumar, Arun

The error you are encountering (com.microsoft.dataflow.broker.InvalidOperationException: Only one valid authentication should be used for linked service) is because the linked service in Synapse is configured with two authentication methods: SQL Authentication (user/password) and Managed Identity. This dual authentication configuration causes conflicts in Data Flows, which expect a single clear authentication method.

To resolve this issue, you can try to set the "Connection Version" to "Legacy" in the linked service configuration. This change forces the Data Flow to use the traditional connection method, avoiding the authentication conflict.

Select "1.0" (Legacy) Option - Make sure the "1.0" option is selected instead of "2.0". This will configure the linked service to use the legacy connection type.

I hope this information helps. Please do let us know if you have any further queries.

Kindly consider upvoting the comment if the information provided is helpful. This can assist other community members in resolving similar issues.

Thank you.

• @Chandra Boorla We are using version 1.0 only, but still getting the same error.

@Kumar, Arun

If you are already using Version 1.0 (Legacy) but still getting the error, it indicates that your linked service is configured with conflicting authentication methods (SQL Authentication and Managed Identity), which is not supported in Data Flow. Even though the test connection works, Data Flow strictly requires only one valid authentication method.

Here are some troubleshooting steps that might help you:

Ensure only one authentication method is used - If using SQL Authentication, make sure both the username and password are configured, either directly or through Key Vault. If using Managed Identity, ensure the linked service is set to "Managed Identity", and no username/password fields are filled.

Double-check linked service configuration - Make sure the linked service is not set to use both Managed Identity and SQL Authentication at the same time. If using Key Vault, ensure that the credentials are set for only one authentication method.

Clear cached credentials - If you recently made changes, clear your browser cache or use Incognito mode to avoid cached settings.

Re-test your data flow - Save your changes and re-run the Data Flow to confirm the issue is resolved.

For additional information, please refer the below Microsoft documentations:

• SQL Authentication in Azure Synapse Analytics
• Copy and transform data in Azure Synapse Analytics by using Azure Data Factory or Synapse pipelines

I hope this information helps. Please do let us know if you have any further queries.

Thank you.

@Chandra Boorla All credentials are coming from Key Vault like username, password, host and database name. There is no option explicitly to chose SQL Authentication alone in Version 1.0 linked service, both comes together ("SQL authentication or Managed identity")

@Kumar, Arun

Thanks for the clarification, this is an important detail.
You're absolutely right: when using Linked Service version 1.0 (Legacy) for Azure SQL Database in Synapse, there is no explicit dropdown to select SQL Authentication vs. Managed Identity. Instead, the authentication method is implicitly determined based on which credentials are provided, especially when sourcing values from Azure Key Vault.

Currently, your linked service is:

Version: 1.0
Credential Source: Azure Key Vault
Authentication type: SQL Authentication or Managed Identity

How it behaves in version 1.0:

Synapse attempts to auto-resolve the authentication method:

If both username and password are provided via Key Vault → it uses SQL Authentication.
If those values are not provided but Managed Identity is configured → it uses Managed Identity.
If there’s a mix or conflict (e.g., password missing or both methods partially configured) → you may get runtime errors in Data Flows, even though the test connection may still succeed.

Recommended Actions:

Please choose one clear path for authentication to avoid this conflict:

Option 1 – Use SQL Authentication only:

Ensure both username and password secrets are correctly configured in Key Vault.
Do not assign or use Managed Identity on this connection.
Keep the current setting ("SQL Authentication or Managed Identity").

Option 2 – Use Managed Identity only:

Remove any username/password secrets from the Key Vault for this connection.
Ensure your Synapse workspace's Managed Identity is granted access to the Azure SQL Database.
Synapse will then auto-resolve to use the Managed Identity.

Alternatively, consider switching to Linked Service version 2.0, which allows you to explicitly select the authentication type (SQL Authentication, Managed Identity, Service Principal, etc.), and avoids this ambiguity.

I hope this information helps. Please do let us know if you have any further queries.

Thank you.