The refresh data option causes a cube’s data to be cleared and reloaded and its aggregations recalculated. This option is appropriate when the underlying data in the data warehouse has changed but the cube’s structure remains the same. This option is faster than processing the cube because aggregation tables do not have to be redesigned.
The refresh data option can be performed while users continue to query the cube; after the refresh has completed users will have access to the updated data without having to disconnect and reconnect.