When do u we use dynamic cache and when do we use static cache in an connected and unconnected lookup transformation?

We use dynamic cache only for connected lookup. We use dynamic cache to check whether the record already exists in the target table are not. And depending on that, we insert,update or delete the records using update strategy. Static cache is the default cache in both connected and unconnected. If u select static cache on lookup table in infa, it own't update the cache and the row in the cache remain constant. We use this to check the results and also to update slowly changing records