How to fix Error 4915 on Windows Server 2025 / Windows 11

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Why This Error Happens

This error occurs when you attempt to align a table and an index on the same partition function, but the underlying partition function uses a different data type than what the index’s partitioning scheme expects. SQL Server requires that the parameter type of the partition function for a table matches exactly with the parameter type of the partition function used for any aligned index, since mismatched types (e.g., int vs bigint, or datetime vs datetime2) break the alignment contract needed for partition switching and metadata-only operations. This typically surfaces during CREATE INDEX, ALTER TABLE...SWITCH, or rebuild operations when schemas have drifted over time or were migrated from an older SQL Server version.

Step-by-Step Resolution Guide

Step 1: Identify the Conflicting Partition Functions

  • Run the following query to list all partition functions and their parameter data types:
SELECT pf.name AS PartitionFunction, pf.function_id, 
       t.name AS DataType, pp.system_type_id
FROM sys.partition_functions pf
JOIN sys.partition_parameters pp ON pf.function_id = pp.function_id
JOIN sys.types t ON pp.system_type_id = t.system_type_id;
  • Compare the data type used by the table’s partition scheme against the one used by the index you are trying to create or align.

Step 2: Check the Index and Table Partition Scheme Alignment

  • Use sys.indexes and sys.partition_schemes to confirm which scheme each object is tied to:
SELECT i.name AS IndexName, ps.name AS SchemeName, pf.name AS FunctionName
FROM sys.indexes i
JOIN sys.partition_schemes ps ON i.data_space_id = ps.data_space_id
JOIN sys.partition_functions pf ON ps.function_id = pf.function_id
WHERE i.object_id = OBJECT_ID('YourSchema.YourTable');
  • Confirm whether the index was created against a legacy partition function with a mismatched type (common after restoring databases from SQL Server 2016/2017 instances onto SQL Server 2025).

Step 3: Recreate the Partition Function with Matching Data Type

  • Drop the index that references the mismatched function (ensure you have a backup/script of the original index definition first):
DROP INDEX YourIndexName ON YourSchema.YourTable;
  • Create a corrected partition function using the exact same data type as the table’s partition function:
CREATE PARTITION FUNCTION PF_Corrected (bigint)
AS RANGE LEFT FOR VALUES (100, 200, 300);
  • Recreate the partition scheme referencing the new function, then rebuild the index against this aligned scheme.

Step 4: Rebuild and Validate the Index

  • Recreate the index explicitly specifying the corrected partition scheme:
CREATE NONCLUSTERED INDEX IX_YourIndex
ON YourSchema.YourTable(YourColumn)
ON PS_Corrected(YourPartitionColumn);
  • Monitor the SQL Server Error Log (via xp_readerrorlog or Event Viewer under “Applications and Services Logs > Microsoft > SQL Server”) to confirm Error 4915 no longer appears during the operation.

Alternative or Verification Steps

  • Re-run the original CREATE INDEX or ALTER TABLE...SWITCH statement that originally failed; if it completes without throwing Error 4915, the type mismatch has been resolved.
  • If recreating the partition function isn’t feasible due to downstream dependencies, consider using ALTER TABLE...SWITCH with an intermediate staging table that explicitly matches both the table and index partition function data types before merging data back.