How to fix Error 4995 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 4995 – Vardecimal Storage Format Not Available in System Databases

Why This Error Happens

This error occurs because the sp_db_vardecimal_storage_format procedure is being executed against a protected system database such as master, model, msdb, or tempdb. SQL Server intentionally restricts vardecimal storage format changes to user-defined databases, as system databases rely on a fixed, internal storage structure to maintain engine stability. Attempting to enable this legacy storage feature on a system database is blocked at the engine level and is not a permissions or corruption issue, but a hard architectural limitation.

Step-by-Step Resolution Guide

Step 1: Identify the Target Database Context

  • Check the exact database name referenced in the error message (%.*ls) to confirm it is indeed a system database.
  • Run SELECT name, database_id FROM sys.databases; in SQL Server Management Studio (SSMS) to cross-reference system vs. user databases.
  • Confirm you did not accidentally run the script while connected to master instead of your intended user database.

Step 2: Correct the Database Context Before Re-running the Command

  • Open a new query window in SSMS and explicitly switch context using USE [YourUserDatabase]; before executing the procedure.
  • Re-run the command: EXEC sp_db_vardecimal_storage_format 'YourUserDatabase', 'ON';
  • Avoid running maintenance or storage-format scripts inside master, model, msdb, or tempdb entirely.

Step 3: Audit Automation Scripts and Deployment Pipelines

  • Review any PowerShell, DACPAC, or SSDT deployment scripts running on Windows Server 2025 that may loop through sys.databases and apply this setting to all databases, including system ones.
  • Add a filter condition such as WHERE database_id > 4 to exclude system databases (master, tempdb, model, msdb) from the loop logic.
  • Update any scheduled SQL Agent Jobs to explicitly target only intended user databases.

Step 4: Consider Modern Alternatives (Since Vardecimal Is Deprecated)

  • Since SQL Server 2016+ (including SQL Server 2025), Vardecimal storage format is a legacy feature superseded by Row/Page Compression.
  • On your user database, use ALTER TABLE YourTable REBUILD WITH (DATA_COMPRESSION = ROW); instead for better storage efficiency and native engine support.

Alternative or Verification Steps

  • Verify the Fix: Run EXEC sp_db_vardecimal_storage_format 'YourUserDatabase', 'STATUS'; to confirm the setting applies successfully without throwing Error 4995.
  • Alternative Solution: If vardecimal format is not strictly required, skip it entirely and implement DATA_COMPRESSION = PAGE on the specific table, which achieves similar storage savings and is fully supported in Windows Server 2025 environments without the system database restriction.