The enterprise data warehouse database is the most critical. Recovering this database requires more work and data transformations than recovering data in the data marts. If you lose the enterprise database, the data marts cannot gather new data until the enterprise data warehouse is back online. You should also save any transformation scripts or DTS packages that can help you rebuild the database if the restore process fails.
You should use the incremental update processing method to add new data. This method uses partitions and affects the cube minimally.
You should migrate the OLAP Services Repository database to SQL Server to maximum database integrity. Migrating this repository also minimizes administrative overhead by allowing you to administer the OLAP Services Repository with the same backup and restore methods that you use in SQL Server.