If the database is in-memory only, Sync has no effect and always succeeds.

Flushing cached information to disk only minimizes the window of opportunity for corrupted data. Although unlikely, it is possible for database corruption to occur in the event of a system or application crash while writing data to the database. To ensure that database corruption never occurs, applications must either use transactions and logging with automatic recovery, or edit a copy of the database and then replace the corrupted database with the updated copy once all applications using the database have successfully called Close()()().