In BAM, instead of waiting for the execution of data analysis task to update the cube aggregations at scheduled intervals, one can define specific slices of data to be aggregated in real-time. For example, in a departmental store scenario, a store manager may want to know what the sales of a promotional item is. Typically, he may have to wait for the report on the next day because the cube aggregations are updated daily at midnight. With the real-time aggregation feature in BAM, he may query the real-time views via Excel pivot tables, to know the up-to-date (to the minute) sales of the promotional item for today. In BizTalk 2006, the user may also query via the BAM portal and even set alerts based on a threshold.

BAM updates the real-time aggregation tables as and when the data arrives at the BAM infrastructure. To maintain this table, an online window is defined. This online window defines how much aggregate data is to be kept in the tables. Note that if the online window is set to (say) 1 day, only data a day earlier till now would be aggregated. Typically, you would want to set the online window slightly larger than the time span the queries are based on. In BizTalk 2004, one can pre-defined the online window in the BamConfiguration.xml and this will be applied when the BAM infrastructure is created. If this online window for the real-time aggregation needs to be changed, the corresponding row in the bam_metadata_RealTimeAggregations table can then be modified. In BizTalk 2006, the option SetRTAWindow in bm.exe should be used instead of modifying the table directly and the default online window is 3600 minutes which is the same as in BizTalk 2004.

More information can be found at: http://www.msdn.microsoft.com/library/default.asp?url=/library/en-us/sdk/htm/ebiz_prog_bam2_qkng.asp