How to fix Error 4807 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 4807 – Invalid BCP Row Length

Why This Error Happens

Error 4807 occurs when the bulk copy (bcp) client sends a row length that falls below the minimum size SQL Server 2025 requires to process the bulk insert operation. This typically results from a mismatched or corrupted format file, an outdated bcp utility version that doesn’t align with the target table schema, or incorrect field terminators/row terminators defined in the data file. It can also surface when a custom application uses a legacy or unsupported client API (such as DB-Library) instead of ODBC or OLE DB to perform the bulk copy operation.

Step-by-Step Resolution Guide

Step 1: Verify the BCP Format File and Data File Structure

  • Open the .fmt format file used in the bulk copy operation and confirm the column count matches the destination table schema exactly.
  • Check that field terminators (e.g., comma, tab) and row terminators (e.g., \r\n) are correctly defined and not accidentally stripped during file transfer.
  • Run bcp [DatabaseName].[Schema].[TableName] format nul -c -t, -r\n -T -f newformat.fmt to regenerate a fresh format file for comparison.

Step 2: Update or Reinstall the BCP Utility and Native Client

  • Confirm you are using the bcp utility bundled with SQL Server 2025 tools, not a legacy version from SQL Server 2014/2016 installations.
  • Navigate to C:\Program Files\Microsoft SQL Server\Client SDK\ODBC\180\Tools\Binn\ on Windows Server 2025 and verify bcp.exe version using bcp -v.
  • Download and install the latest Microsoft ODBC Driver 18 for SQL Server if the version is outdated.

Step 3: Switch to a Supported Client API

  • If a custom application is triggering this error, confirm it is not using the deprecated DB-Library API, which Microsoft no longer fully supports for bulk operations in SQL Server 2025.
  • Reconfigure the application connection string to use ODBC Driver 18 or OLE DB Driver 19 for SQL Server.
  • For PowerShell-based imports, use the Write-SqlTableData cmdlet or Invoke-Sqlcmd with the -InputFile parameter instead of raw bcp calls where possible.

Step 4: Validate Table Schema and Minimum Row Size

  • Run sp_help [TableName] in SSMS to review the exact byte-length requirements of each column, especially fixed-length types like char, binary, and datetime.
  • Ensure your source data file does not contain truncated or empty rows that fall below this calculated minimum row size.

Alternative or Verification Steps

  • Re-run the bulk copy operation with the -e error.log flag to capture detailed row-level errors: bcp [TableName] in datafile.csv -c -t, -S servername -T -e error.log.
  • If the issue persists, test the import using the BULK INSERT T-SQL command instead of the command-line bcp utility, as it often provides more granular error context tied directly to the SQL Server engine.