jQuery.post potential max_user_connections error

jQuery.post potential max_user_connections error

If I am making a request via jQuery.post to run a PHP function it is possible on a heavily trafficked site for an Apache server to have reached the limit defined by max_user_connections. This means that a new process cannot be created, that is the PHP function will not be executed.

What does jQuery do if this occurs?
1) does it just continue on without having executed the function so that the user wouldn't even notice that something has failed?
2) does it cause the script to crash and therefore cause a page or browser problem?
3) some other problem?

If 2) or 3) is true is there any code I can add to avoid problems?