The best way to explain this is with an example:
Alice can reach a folder named "Kick-off meeting" which belongs to another user, Bob. Alice then creates a document called "summary.docx" in this folder, and is thus owner of this file without being owner of the parent folder.
The way we perform document migration, including permissions, is the following:
- For each user, we compute all owned folders, and for each of them we migrate all owned files.
- Then, for each of the migrated folders and files, we retrieve and apply the corresponding permissions.
Based on that logic, here is what will occur during the migration:
- During Alice's migration, we will not migrate the "Kick-off meeting" because it doesn't belong to Alice, and consequently, we will not migrate "summary.docx".
- During Bob's migration, since "Kick-off meeting" belongs to Bob, we'll migrate it, but since "summary.docx" doesn't belong to Bob, we will not migrate this file.
Note: This behavior explains how MigrationWiz behaves in default mode. An alternative and recommended approach is to migrate from Google Drive to OneDrive for Business using moderate mode. KB005034 explains this further.