without using update t/mation also we can update. in 
session properties select update against treat source rows 
as. this wud definitely help you.

push down is a function of 8.1 version of informatica. it 
reduces the load on informatica server.

unconnceted obviously bcoz not connected with the data flow 
and uses only static cache.
also it can be called as many times in a mapping as a 
result of an expession.

reach me on 9866188658.

By using Update override option in Target table we can 
update the table

We can use update override in the target table in mapping.

Push Down Optimization is an optimizing technique in
informatica 8. Integration service pushes the transformation
logic either to the source database or to the target
database rather than executing the logic by itself. 

I think dynamic lookup gives a better performance since it
allows us to tune the cache sizes(index and data).