Workload Management and Service Classes
Service classes define limits on groups. You can design service classes using these limits.
When a user is present in multiple groups with different service class limits, the least restrictive limit for each parameter will be applied. For example, if User A is in groups G1 and G2, which have service class time limits of 10 seconds and 20 seconds, when User A runs a query, the query will have a time limit of 20 seconds. This behavior is slightly different for concurrency. If the service class concurrency limits for the user’s groups are 1 and 2, a query can use a concurrency slot from either service class. A user with multiple service classes can experience a query executing with a slot from one service class, but using time limit or other limits from a different service class. Additionally, service class concurrency limits will not be applied when a query affects only system tables.
A walkthrough of designing a set of service classes for workload management is available in the Workload Management Walkthrough
See Users, Groups, and Service Classes for service class related DDL command reference such as creating, altering, and applying a service class.