You can replace an aggregation by clearing the existing aggregation and materializing a different selection of aggregate views. You can perform a new aggregate view selection and materialization process, or you can run an aggregation script. Consider replacing the aggregation in the following situations:
To fine-tune the selection of aggregate views to improve performance. See Fine-Tuning Aggregate View Selection.
To create aggregations optimized for different database retrieval situations, such as for generating reports or user queries.
To optimize an aggregation after significant growth in database size. Gradually, as the size of a database increases, an aggregation can become less efficient. Consider replacing an aggregation when performance degradation is noticeable or when the database size increases to about 150% of its original size.
To optimize aggregations for new or different operational environments, such as memory and disk resource availability changes.
You must replace an aggregation and associated aggregation scripts after the number of levels in a dimension has been changed or one or more dimensions have been added or removed from the outline. See Performing Database Aggregations and Working with Aggregation Scripts.