Difference between Save and Save All ?

Hello

What is the difference between Save and Save All ?

• In Teamcenter10+NX9 it takes very long 30-45mins to save a *large* assembly. Is it normal ?
• When I press Close All it takes also that long...I believe it is same as Save All ?
• How to make *large* assemblies containing 400-600 parts save and close more faster ?

If you deal with large assemblies how long does it take for you to open and save it ?

 I experience this situation: (NX9 and Teamcenter10)

1. Opening an assembly(500parts) takes 15-20mins.
2. Closing the assembly takes 30-45min.

So as an example modifying a one part in the assembly takes 1h5min+the time it takes to make the modifications to the part.