The STGC enumeration constants specify the conditions for performing the commit operation in the IStorage::Commit and IStream::Commit methods.
public enum STGC
Microsoft Windows 2000/XP: Indicates that a storage should be consolidated after it is committed, resulting in a smaller file on disk.
Commits the changes to a write-behind disk cache, but does not save the cache to the disk.
You can specify this condition with STGC_CONSOLIDATE or some combination of the other three flags in this list of elements.
Prevents multiple users of a storage object from overwriting each other's changes.
The commit operation can overwrite existing data to reduce overall space requirements.