Microsoft admits SQL Servers might wobble after October update

Encountered some odd SQL Server connection behavior since the October update? There might be a culprit... Microsoft has admitted that a change has caused linked server queries to fail to close connections.

Linked servers via OLE DB providers have been around for years and are a useful way of, for example, using additional data sources in queries. Once a provider is added, SQL Server can open a connection to grab data, and close it again when the query is complete. Or, at least, that's the theory.

The problem is that after the October 13 (KB5126646) update, connections created by SQL Server linked server queries might remain open. According to Microsoft, "As additional queries are performed, connections to external databases can accumulate instead of closing as expected.

"This can slow or degrade server performance after prolonged run time."

You think? Administrators will likely have already noted a suspicious number of open connections to external databases on affected systems.

Microsoft said the issue affects SQL Server linked server queries that use OLE DB providers to connect to external databases. It gave PostgreSQL and Oracle as examples of connections known to be affected.

And the fix? "If idle connections can be identified, it is possible to manually close them to temporarily relieve server load.

"It is also possible to temporarily restore system stability by restarting the SQL service."

The Windows behemoth went on to state the obvious: "However, these steps can also interrupt active queries or transactions, and the problem can resurface again after sufficient operation time."

Bouncing a SQL Server to deal with connection leakage is less than ideal, although it would at least be a good failover test and, let's face it, having to restart Microsoft services regularly is something many administrators will be all too familiar with.

There is a mitigation available, although only through Microsoft support for business. Otherwise, an out-of-band update should be along within the next few days to deal with the problem.

According to Microsoft, the technical glitch affects every version of Windows except Windows 11 26H2, stretching back to Windows 10 1809 and LTSC 2019, and Windows Server from 2025 back to 2012.

Microsoft, or rather the unfortunate souls responsible for administering their server products, has not had the best time of late. The October 2026 Windows Server update left some Exchange Servers wobbling until either a Registry edit was made or a fix was applied as part of the November update. (R)