A throttle limits the number of queries running at one time on an Teradata Aster system.
You specify the predicate when you create the throttle and it must be a valid SQL WHERE clause. You can use existing UDFs, SQL operators, workload management attributes, and AND and OR conjunctions.
You set a concurrency limit by specifying the maximum number of queries matching the predicate that can run at a given moment. Each query must pass all predicates before being admitted to the system. Queries submitted after the limit is reached are queued. Throttles are known as admission limits in the Teradata Aster® Database User Guide.
- A specific database to which the client is connected.
- A set of database roles of which the current user is a member, such as users who have been granted the admin role.
- A statement type, such as SELECT, DROP, EXPLAIN, REVOKE, SHOW, and others.
- Elapsed time, such as limiting a specific statement that has executed over 30 minutes by a user that is part of a group.
Global throttles limit the maximum number of concurrent queries to a value you specify regardless of the attributes of the queries. If the number of running queries reaches the value you set, new queries are queued. If the global throttle limit is not reached, the regular throttles setting determines if and when a query is admitted to the system. Global throttles are known as global admission thresholds in the Teradata Aster® Database User Guide.