How to fix Error 6955 on Windows Server 2025 / Windows 11

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Why This Error Happens

Error 6955 occurs in SQL Server Analysis Services (SSAS) when the metadata for a dimension attribute is malformed, typically because the KeyColumns, NameColumn, or ValueColumn bindings reference a data source column that no longer exists, has an incompatible data type, or has been duplicated across attributes. This often happens after a schema change in the underlying relational database that was not propagated to the SSAS project, or after a corrupted deployment/XMLA script introduced invalid attribute XML. It can also surface when a dimension is restored or migrated from an older SQL Server version into SQL Server 2025 and the attribute definitions are incompatible with the newer engine’s validation rules.

Step-by-Step Resolution Guide

Step 1: Identify the Faulty Attribute and Dimension

  • Open the SSAS error log or SQL Server Profiler trace to capture the full error text, which includes the specific attribute name (%s) and the dimension it belongs to.
  • In SQL Server Management Studio (SSMS), connect to the Analysis Services instance and locate the affected dimension under Databases > [YourDB] > Dimensions.
  • Cross-reference the attribute name against the source table schema in SQL Server 2025 to confirm the column still exists and matches the expected data type.

Step 2: Repair the Attribute Binding in SQL Server Data Tools (SSDT)

  • Open the Analysis Services project in SSDT (Visual Studio) that corresponds to the deployed database.
  • Navigate to the Dimension Designer, select the problematic attribute, and inspect the KeyColumns, NameColumn, and ValueColumn properties in the Properties pane.
  • Remove any reference to a non-existent or renamed column, then remap it to the correct source column using the Data Source View (DSV).
  • Rebuild the DSV (Refresh option) to sync table/column metadata if the underlying SQL Server table structure changed.

Step 3: Clear Corrupted Metadata and Redeploy

  • Delete the corrupted dimension object from the SSAS database via SSMS (right-click dimension > Delete) to remove any residual invalid XML definitions stored in the OLAP store.
  • From SSDT, redeploy the corrected project using Build > Deploy, pointing to the correct target server (localhost or the named SSAS instance on Windows Server 2025).
  • If deployment fails, validate the project XML manually by opening the .dim file in a text editor and checking the <Attributes> node for duplicate AttributeID entries or malformed <KeyColumns> tags.

Step 4: Reprocess the Dimension and Cube

  • In SSMS, right-click the redeployed dimension and select Process using the Process Full option to rebuild all attribute hierarchies from scratch.
  • Once the dimension processes successfully, reprocess any dependent cubes (Process Full at the cube level) to ensure measure groups relink to the corrected dimension attributes.

Alternative or Verification Steps

  • Run a test query against the dimension using MDX (SELECT {[Attribute].MEMBERS} ON 0 FROM [Cube]) in SSMS to confirm the attribute now returns valid members without errors.
  • If the issue persists after redeployment, restore the SSAS database from a known-good backup taken before the schema change, then manually reapply only the valid schema updates through SSDT rather than a direct XMLA alter script.