Cube failure due to data length issue

Kayal 0 Reputation points
2026-09-24T10:17:43.5566667+00:00

Cube failure with below error

“Errors in the OLAP storage engine: An error occurred while the 'Diagnosis' attribute of the 'DimUniqueDiagnosis' dimension from the 'CQMC_RBGBGWS_Analysis_Test' database was being processed.”

We are doing SL3 to SL4 server migration in SL3 server the same set of data is working fine but in new SL4 server we got this issue. Old SSAS server version is 13.0 and new server version is 17.0.. What will be fix for above error quick fix may be the reverting back to the old version?

 

SQL Server Analysis Services
SQL Server Analysis Services

A Microsoft online analytical data engine used in decision support and business analytics, providing the analytical data for business reports and client applications such as Power BI, Excel, Reporting Services reports, and other data visualization tools.

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  1. Rukshan edirisinghe 2,365 Reputation points
    2026-10-20T04:34:57.0766667+00:00

    Hi @Kayal

    That first line is only the generic part of the error. The real reason is usually in the lines underneath it in the processing window. Since the same data works on the 13.0 server, I'd compare how the Diagnosis attribute is defined against what the new server now reads from the source before rolling back.

    1. Process the DimUniqueDiagnosis dimension on its own (Process Full) in SSMS and expand every error line. Look for words like "size", "truncated", "duplicate attribute key" or "collation".
    2. In the cube project, open the dimension, select the Diagnosis attribute and check KeyColumns and NameColumn. Compare their DataSize to the length of the source column. If the source is longer (for example it was widened or now returns nvarchar(max)), increase DataSize to match.
    3. Right-click the Data Source View and select Refresh so it picks up the current column types, then redeploy and process again.
    4. Check that the new SSAS instance uses the same collation as the old one. A different collation can turn values that were distinct before into duplicates.
    5. For testing only, you can change the dimension's error configuration to report the failing rows. Don't leave keys ignored in production.

    Take a backup of the SSAS database before you redeploy, so you can always restore the working version.

    Could you share the full error lines that appear below the one in your post?

    If this got the cube processing on the new server, please consider accepting it as the answer. If the inner error says something different, let me know and I'll be happy to keep helping.

    Reference:

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