Workload Management and Service Classes
Service classes define limits on groups. You can design service classes using these limits.
For details on using the CACHE_MAX_BYTES and CACHE_MAX_TIME parameters, see Result Set Caching.
For details on using the LOW_LATENCY parameter, see Low-Latency Settings.
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.
If you set a service class at the session or query level, the system uses the value set by that service class, with the query-level service class taking precedence.
Otherwise, if you set a value for this parameter at the session or query level, the system uses the most restrictive of the two.
If the Ocient System chooses the value from multiple service classes, the system takes the least restrictive value from all service classes. Then, the system takes the most restrictive of that value and the query or session level value, if it exists.
This selection does not hold true for parameters related to result set caching: cache_max_time and cache_max_bytes. For details about the behavior, see Result Set Caching.
If you choose a service class using statement text matching, the system compares its value to the query or session level value, and the system does not review any other service classes.
A tutorial for 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 statement references such as creating, altering, and applying a service class.