Incremental Cube Processing

AS2005 will NOT process aggregations automatically when you process the partition. During used partition processing it used to process the data and it also built the aggregations for that partition. It is changed in AS2005. You can process partition incrementally using "Process Incremental" option. If you want to build index you have to do that using "Process Index" option.

If you wish, you can put these two in 2 separate steps within SSIS after data is loaded.

Its all about how quickly you want the data presented to the users. If you do the Process Incremental first and made the data available for users first and then build the aggregations while users are using the data. This way will give you maximum availability, but impacts performance while building aggregations and indices. UI in SSMS does not support "Process Incremental" and "Process Index" in one single transaction. You can achieve that using simple XMLA scripts as shown below:
http://www.smart-bi-solutions.com/BlogStuff/incremental_process.xmla

This example uses Adventure Works. ProcessAdd and ProcessIndexes are the key things to look out for in the XMLA doc.

Thanks
Sutha