The aggregates in APO are not the same as those in the Business Information Warehouse (BW), but they have the same purpose: to speed up data access and therefore increase performance. SAP recommends that you use aggregates in Demand Planning.
These aggregates are sometimes referred to as persistent aggregates, in particular when talking about detail and aggregate levels in interactive planning.
An APO aggregate contains a subset of the characteristics in the master planning object structure. The creation and use of aggregates is optional. The data is always saved on the lowest level of detail. If aggregates exist, the system saves the planning data on the defined aggregate levels as well as on the lowest level of detail. The data is saved twice, but consistently; that is, the sum of the details equals the aggregate value.
SAP recommends that the aggregates you build in APO for planning data also exist in BW for actual data.
If you want to save fixed values at aggregate level ; that is not at detail level of the master planning object structure, in a planning book, you must create aggregates for this level. Otherwise the data is only saved at detail level.
You cannot form aggregates for navigational attributes
Aggregates are discussed in detail in OSS note 503363. SAP recommends that you read this note thoroughly before configuring your master planning object structures and aggregate hierarchy.