The config cache is where we cache configuration information (stored in the config database) on each server in the farm.  Caching the data on each server prevents us from having to make SQL calls to pull this information from the configuration database. It is full of XML files containing configuration objects.  The SharePoint configuration cache is where configuration information from the SharePoint configuration database is stored on each server in the farm.  Caching the data from the config database as XML files on the web front ends and application servers prevents multiple calls to SQL Server thus improving performance.  This is a feature in WSS & MOSS 2007 as well as SharePoint 2010.

Sometimes this cache can become corrupted. This issue can come up when developing timer job definitions . These definitions use this cache, so everytime you deploy new versions of the assemblies, you’ll have to clear the cache.  Also, when the cached data becomes out of sync with what’s in the configuration database, timer jobs may start failing.  This will occur if the contents of the file system cache on the front-end servers are newer than the contents of the configuration database, so after you perform a system recovery you may have to manually clear the file system cache on a server as well.  Another of the reasons your cache could be out of sync is if the Timer service on your servers was stopped or failed unexpectedly.

If you are experiencing issues with WSS/MOSS/SharePoint timer jobs failing to complete or you are receiving errors trying to run psconfig, clearing the configuration cache on the farm or a problem server is a possible method for resolving the issue.

To clear the configuration cache, Follow these steps:

First, stop the timer service on the server.

Next, navigate to: C:\ProgramData\Microsoft\SharePoint\Config

You will see 2 folders in this directory.  Both are named with GUIDs.  Open them up and be sure NOT to touch the one with the PERSITEDFILEs.  Find the one that is filled with XML files.

In the directory with the XML config files, delete everything except cache.ini.  Then, edit the cache.ini file so that it just contains one line with a “1″.

Now, restart the Timer service on the server and watch for the folder to start repopulating the folder.

If this is a single-server farm, or if there is only one problem server, this may be all you need but I recommend doing it on all the web front ends and the application servers in the farm.

Once you are done, go into Central Admin and check your timer job status.  You should see a timer job for “Config Refresh”.  Verify that this job shows a status of succeeded.

Now you’re good to go.