Applies to 5.3.x and 6.0.x.
Recently discovered issue with disabled “registry” cache can potentially increase chattiness of your Sitecore web server with SQL Server.

Basically what happens is regular SQL selects from ‘Properties’ table that stores user-based registry settings for a current site. The call is initiated by Item.DisplayName property which is frequently used on the delivery boxes too. This is not a problem for the authoring environments that operate in the context of “shell” site by default since the registry cache is enabled there. This is not the case for “website”* as two places where this may be changed contain zeros:

<site name="website" … registryCacheSize="0" …  />

<cacheSizes>   <sites>     <website>      <html>10MB</html>      <registry>0</registry>      <viewState>0</viewState>       <xsl>5MB</xsl>     </website>    </sites> </cacheSizes>

The way to fix this is to simply adjust the value of registry cache. You can try 1KB and monitor the /sitecore/admin/cache.aspx page to see the actual consumption. From my experience, it is rarely even approaching 1KB in most installations unless you are writing something there with custom code.

This will be officially documented as a known issue and published on SDN.

In meantime, go ahead and put it in your web.config ;-)

* If you have a multisite environment, change this on the level of your custom site definition responsible for the front-end requests. If in doubt, let me know.