How to fix Error 5293 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 5293 – Columnstore Index Dictionary Mismatch

Why This Error Happens

Error 5293 indicates that the nonclustered columnstore index has become logically corrupted — the compressed data values stored in a rowgroup no longer match the entries in their associated dictionary (the structure columnstore uses to encode repeated string/binary values). This typically occurs due to a hardware-level I/O inconsistency, an improper shutdown during a bulk load or index rebuild operation, or a bug-related page corruption that bypassed checksum validation. It can also surface after restoring a database from a backup that was taken while the columnstore index was in an inconsistent state.

Step-by-Step Resolution Guide

Step 1: Confirm the Scope of Corruption

  • Run DBCC CHECKDB ('YourDatabaseName') WITH DATA_PURITY, NO_INFOMSGS, ALL_ERRORMSGS; to confirm whether the corruption is isolated to this single nonclustered columnstore index or is part of a broader disk/storage issue.
  • Review the SQL Server error log (C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Log\ERRORLOG) for correlating I/O warnings (Event ID 823/824) around the same timestamp.
  • Document the exact table and index name reported in the error message for use in later steps.

Step 2: Drop and Recreate the Affected Nonclustered Columnstore Index

  • Since Error 5293 explicitly states the dictionary cannot be trusted, run:
  DROP INDEX [YourNCCI_IndexName] ON [dbo].[YourTableName];
  • Recreate the index using the original definition:
  CREATE NONCLUSTERED COLUMNSTORE INDEX [YourNCCI_IndexName]
  ON [dbo].[YourTableName] (Column1, Column2, Column3)
  WITH (DROP_EXISTING = OFF, MAXDOP = 4);
  • Monitor sys.dm_exec_requests or the SSMS “Activity Monitor” for progress if the table is large.

Step 3: Validate Underlying Storage Health

  • Open Event Viewer on Windows Server 2025 / Windows 11 and check the System log for Disk or NTFS warnings correlating with the corruption window.
  • Run chkdsk D: /f /r (adjust drive letter to your SQL data volume) during a maintenance window to rule out physical sector errors.
  • If using Storage Spaces Direct or SAN-attached volumes, verify multipathing drivers and firmware are current, as outdated drivers are a common cause of silent I/O corruption.

Step 4: Restore from Backup if Rebuild Fails

  • If DROP/CREATE INDEX fails with the same error or additional corruption errors appear, restore the database (or just the affected filegroup, if isolated) from the last known-good full backup plus transaction log backups.
  • Use RESTORE VERIFYONLY first to confirm backup integrity before applying it to production.

Alternative or Verification Steps

  • After recreating the index, re-run DBCC CHECKDB with the DATA_PURITY option to confirm no residual corruption remains, and execute a sample SELECT with a WHERE clause targeting the previously affected rowgroup to confirm query plans use the columnstore index without errors.
  • If corruption recurs on the same table shortly after rebuild, treat it as a hardware/storage reliability issue rather than a SQL Server bug — escalate to your storage/hardware vendor and consider moving the database files to a different physical disk temporarily to isolate the fault.