Adrotate doesn't close mysql connections?

Every connection AdRotate makes to MySQL goes through $wpdb (The wordpress database class).

https://dev.mysql.com/doc/refman/5.5/en/too-many-connections.html

A common thing that happens on cheap shared hosting is that the webhost puts too much people on the same server or shares users/mysql instances across multiple users. This will work against you in many ways, one of which a stupidly small pool of connections.

Talk to your webhost about lifting or removing the limitation. Or better yet, upgrade to something better than what they offer.

Sorry for that post. It was not AdRotate causing the troubles. It was the W3 Total Cache plugin.

Isn’t W3 Total Cache designed to lessen overall queries?

No it’s not designed for it, it can if you choose to and it’s possible. Caching plugins are not a silver bullet, instead they allow you to take your hardware to its limit.

Anyway, caching pages will reduce the work PHP and MySQL have to do, but low traffic sites will often remain uncached without priming being used.

If you write me about specific issues with your site we’ll be able to help.

Frederick – So his site is/was likely not optimized/configured very well with your plugin then?
Or how should I see that?

Yes, basically. Unfortunately, there are some starting points, but a fully optimized site requires some testing and investigation.