How to fix Error 4993 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: Error 4993 – ALTER TABLE SWITCH Failure Due to Large Value Types Out Of Row Mismatch

Why This Error Happens

This error occurs when the source and target tables involved in an ALTER TABLE SWITCH operation have mismatched large value types out of row settings, which controls whether large object (LOB) data types like varchar(max), nvarchar(max), varbinary(max), and xml are stored in-row or pushed to separate LOB pages. SQL Server enforces strict schema and storage parity between partitions during a switch operation because the underlying physical storage structure must be identical for the metadata-only switch to succeed. This mismatch typically happens when one table was created or altered with sp_tableoption explicitly set, while the other retained the default setting.

Step-by-Step Resolution Guide

Step 1: Identify the Current Table Settings

  • Open SSMS or Azure Data Studio connected to your SQL Server 2025 instance.
  • Run the following query to check the current setting on both tables:
SELECT large_value_types_out_of_row 
FROM sys.tables 
WHERE name IN ('SourceTableName', 'TargetTableName');
  • Note the Boolean value (0 or 1) returned for each table; these must match exactly before proceeding.

Step 2: Align the Table Option Using sp_tableoption

  • Execute sp_tableoption on the table with the mismatched setting to bring it in line with the other.
  • Example command to set the option to match (replace 1 with 0 if needed):
EXEC sp_tableoption 'dbo.SourceTableName', 'large value types out of row', '1';
  • Run this on whichever table (source or target/partition) currently has the incorrect value based on the Step 1 results.

Step 3: Rebuild Affected Indexes

  • After changing the table option, existing LOB data pages are not automatically reorganized, so rebuild all indexes on the modified table to force storage consistency.
  • Run the following for each index, or use ALTER INDEX ALL:
ALTER INDEX ALL ON dbo.SourceTableName REBUILD;
  • This step is mandatory on Windows Server 2025 instances using the latest SQL Server 2025 storage engine updates, as cached LOB pointers can otherwise persist.

Step 4: Re-run the ALTER TABLE SWITCH Command

  • Execute your original ALTER TABLE ... SWITCH statement again now that both tables share identical LOB storage settings.
  • Monitor the SQL Server Error Log (C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Log\ERRORLOG) for confirmation that no further 4993 errors are raised.

Alternative or Verification Steps

  • Verify success by re-running the sys.tables query from Step 1 on both tables — the large_value_types_out_of_row column values should now be identical.
  • If the switch still fails, drop and recreate the target partition table from scratch using a SELECT INTO from the source table, which guarantees identical storage options, then retry the switch operation.