The initial population of a dimension with data can be achieved by generating a custom procedure and then use the right-click context menu to select the Execute Custom Procedure via Scheduler option.
The dimension should be analyzed once the custom procedure is completed so that the database query optimizer can make use of the indexes.
For smaller dimensions (e.g. less than 500,000 rows) run the normal Update procedure against an empty dimension table. There is however a danger in this action in that the query optimizer will not have any information on the table, and hence will do a full table pass when adding each new row. For a very small dimension this will not be an issue, but it will rapidly become a major problem as the row count increases.
The problem with the initial update is that the database does not know to use the index that has been created for the business key, and hence does a full table pass when attempting to update/insert a record.