Hanu Ch Rao

• Feb 21st, 2007

 

The first time you run a session with incremental aggregation enabled, the server process the entire source. At the end of the session, the server stores aggregate data from that session ran in two files, the index file and data file. The server creates the file in local directory.The second time you run the session, use only changes in the source as source data for the session. The server then performs the following actions:For  each input record, the session checks the historical information in the index file for a corresponding group, then:If it finds a corresponding group – The server performs the aggregate operation incrementally, using the aggregate data for that group, and saves the incremental changes.Else                Server create a new group and saves the record dataWhen writing to the target, the server applies the changes to the existing target.Updates modified aggregate groups in the targetInserts new aggregate dataDelete removed aggregate dataIgnores unchanged aggregate dataSaves modified aggregate data in Index/Data files to be used as historical data the next time you run the session.Each Subsequent time you run the session with incremental aggregation, you use only the incremental source changes in the session.If the source changes significantly, and you want the server to continue saving the aggregate data for the future incremental changes, configure the server to overwrite existing aggregate data with new aggregate data.

Hanu ch Raohanu_ch79@yahoo.com