FetchDataHandler and invalidateCache

If I have a FetchDataHandler via addFetchDataHandler, should it be called as a result of ListGrid invalidateCache being called?

A fetch is being performed when invalidateCache is being called but my handler is not invoked in this situation.

In general (I know it is hard to answer as it may depend on the situation), but if I want to cause a refetch of the data, should I call invalidateCache or fetchData?

Thanks.

I am using SmartClient Version: v9.1p_2014-06-04/Pro Deployment (built 2014-06-04)