Microsoft Confirms Windows Updates Impact SQL Server Performance

Microsoft has confirmed that Windows updates released since the October 2026 Patch Tuesday are causing significant performance and stability issues for SQL Server installations. The problems arise from server queries that fail to close connections to external databases, leading to an accumulation of open connections over time.

Microsoft detailed the issue in a recent Windows release health dashboard update, explaining that the problem specifically impacts SQL Server linked server queries that utilise OLE DB providers to connect to various external databases, with Oracle and PostgreSQL connections among those known to be affected. Administrators in impacted environments may observe a steadily increasing number of open connections to these external databases, even after the associated SQL Server linked server queries have completed their operations. This accumulation gradually degrades server performance.

The bug affects a wide range of systems, including client versions of Windows (Windows 10 and Windows 11) and server operating systems (Windows Server 2012 and later). Microsoft has stated that an out-of-band Windows update will be released within the next few days to provide a definitive fix for the problem.

While a permanent solution is being prepared, Microsoft has offered some temporary workarounds. Administrators can manually close the connections that remain open due to this bug or restart the SQL service. However, these temporary measures come with caveats: restarting the SQL service can interrupt active queries, and the issue is likely to resurface after some time, requiring repeated intervention. For a more robust temporary mitigation, Microsoft advises IT administrators to contact Microsoft Support for Business.

This incident follows other recent stability challenges for Microsoft’s enterprise software. In September, the company provided a temporary workaround for SQL Server crashes observed on some Windows Server 2025 systems. That particular issue, related to memory management changes when the Lock Pages in Memory (LPIM) Windows policy is enabled, could lead to unexpected SQL Server service stoppages or restarts, memory corruption errors, and failures during database maintenance.

Separately, Microsoft also recently acknowledged reports of November 2026 security updates failing to deploy on Windows 11 systems where the October preview update had been installed, with users encountering error codes such as 0x80070306, 0x800f0989, or 0x800f0993. These incidents highlight ongoing complexities in the Windows update ecosystem and their potential impact on critical enterprise applications.