Slow Query Performance

If you find some query suddenly starts running very slow in Access 2010/Windows 7, or it can run slowly on occasion, try to set registry key:

HKLM\SOFTWARE\Microsoft\Office\14.0\Access Connectivity Engine\Engines\ACE\MaxBufferSize to 50000

(HKLM\SOFTWARE\Wow6432Node\Microsoft\Office\14.0\Access Connectivity Engine\Engines\ACE\MaxBufferSize for x64 Windows)

Looks like the same problem exists since Access 2007, see following thread for details:

Access 2007 very slow on Windows 7