Virtual members are properties and collections that are not allocated storage in a repository database. Creating a virtual member is useful if you want to store property values or collection items somewhere other than the repository.
Virtual members are defined on interfaces. You can define nonpersistent members by setting the flag VIRTUAL_MEMBER in the InterfaceMemberFlags enumeration. If this flag is set, the repository engine returns an error if an attempt is made to access this member.
A COM aggregation object must be used to implement the transient storage.