Microsoft SQL Server 2014 Unleashed

Creating a Classifier Function

After you define your resource pools and workload groups, you need to create a classification function that contains the logic to evaluate the connections and assign them to the appropriate workload group. The classifier function applies to each new session connection to SQL Server. Each session stays in the assigned workload group until it terminates, unless is it reassigned explicitly to a different group. There can be only one classifier function active at any given time. If no classifier function is defined or active, all connections are assigned to the default workload group.

The classifier function is a scalar function created with the CREATE FUNCTION statement, which must return a workgroup name as value ...