IRootStorage - Compound File Implementation
COM's compound file implementation of IRootStorage allows you to support saving files in low-memory or low disk-space situations. For information on how this interface behaves, see IRootStorage.
Use the system-supplied implementation of IRootStorage only to support saving files under low-memory conditions.
It is possible to call COM's implementation of IRootStorage::SwitchToFile to do a normal save-as operation to another file. However, applications that do this might not be compatible with future generations of COM storage. To avoid this possibility, applications performing a save-as operation should manually create the second compound file and invoke IStorage::CopyTo. The IRootStorage::SwitchToFile method should be used only in emergency (low-memory or disk-space) situations.