An incremental update is appropriate when new data is to be added to a cube, but existing data has not changed and the cube structure remains the same. The incremental update option adds new data and updates aggregations; it does not require that the cube be processed.
An incremental update does not affect the existing data that has already been processed. It usually requires significantly less time than processing. An incremental update can be performed while users continue to query the cube; after the update is complete, users have access to the additional data without having to disconnect and reconnect.