How to fix Error 7958 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 7958

Why This Error Happens

Error 7958 occurs when DBCC commands (such as DBCC INPUTBUFFER or DBCC OUTPUTBUFFER) attempt to read the input/output buffer of a Session ID (SPID) that is not actively processing a request or has already completed execution. This typically happens because the target session is sleeping, awaiting a client connection, or has been terminated between the time it was identified and the time the DBCC command was executed. It can also occur if the SPID belongs to a system process or background task that does not maintain a readable I/O buffer at that moment.

Step-by-Step Resolution Guide

Step 1: Verify the SPID Is Still Active

  • Run SELECT session_id, status, command FROM sys.dm_exec_requests WHERE session_id = <SPID>; to confirm the session exists.
  • Check if the status column shows “sleeping” or “background” — these states often cannot return buffer data.
  • If the SPID no longer appears in sys.dm_exec_sessions, the connection has already closed and the error is expected behavior.

Step 2: Re-run DBCC Commands Immediately After Capture

  • Capture the SPID using SELECT * FROM sys.dm_exec_connections WHERE session_id = <SPID>; and immediately execute DBCC INPUTBUFFER(<SPID>); in the same batch.
  • Avoid delays between identifying the SPID and running the DBCC command, since the session state can change within milliseconds under high concurrency.
  • Use sys.dm_exec_sql_text(sql_handle) as an alternative method to retrieve the last executed statement without relying on DBCC buffer reads.

Step 3: Check for Blocking or Killed Sessions

  • Query sys.dm_os_waiting_tasks to determine if the SPID was blocked and subsequently rolled back before you issued the command.
  • Review the SQL Server Error Log located at C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Log\ERRORLOG for corresponding KILL or disconnect events around the same timestamp.
  • If the session was manually killed via KILL <SPID>;, this is the expected cause and not a configuration fault.

Step 4: Update SQL Server 2025 Cumulative Updates

  • Open SQL Server Configuration Manager and confirm the current build version under SQL Server Services.
  • Apply the latest Cumulative Update (CU) via Microsoft Update Catalog, as early 2025 builds contain a known timing issue in the DMV snapshot engine affecting transient SPIDs.
  • Restart the SQL Server service through services.msc after the update installs.

Alternative or Verification Steps

  • Re-run the DBCC command against a known active, long-running SPID (e.g., a session executing a large query) to confirm the buffer reads correctly, verifying the fix works for valid sessions.
  • As an alternative, use Extended Events (sqlserver.sql_batch_starting and sqlserver.sql_batch_completed) to capture query text instead of relying on DBCC INPUTBUFFER/OUTPUTBUFFER for transient sessions.