The PowerCenter Integration Service or a relational data source can sort and aggregate records. To sort and aggregate records, the relational data source must also process the WHERE clause.
Enable the data source to sort the records when you run tests on tables that have large volumes of data. To minimize disk input and output, sort the records before the PowerCenter Integration Service reads them.
Enable the data source to aggregate data to reduce the number of rows that the PowerCenter Integration Service reads from the database. For example, you use a COUNT test to compare the number of non null records in two Customer_ID columns. If the database processes the sorting and aggregation, the PowerCenter Integration Service does not have to import all customer records to count them.