You are required to select a service when you connect to the database. The service names for Autonomous Data Warehouse connections are in the format:
These services map to the
HIGH consumer groups.
For example, if you create an Autonomous Database with a Data Warehouse workload type and specify the
database name as
DB2020, your service names are:
If you connect using the
db2020_low service, the
connection uses the
LOW consumer group.
The basic characteristics of these consumer groups are:
HIGH: Highest resources, lowest concurrency. Queries run in parallel.
MEDIUM: Less resources, higher concurrency. Queries run in parallel.
Picking one of the predefined services provides concurrency values that work well for most applications. In cases where selecting one of the default services does not meet your application’s performance needs, you can use the MEDIUM service and modify the concurrency limit. For example, when you run single-user benchmarks, you can set the concurrency limit of the MEDIUM service to 1 in order to obtain the highest degree of parallelism (DOP).
See Change MEDIUM Service Concurrency Limit for more information.
LOW: Least resources, highest concurrency. Queries run serially.
After connecting to the database using one service, do not attempt to manually switch that connection to a different service by simply changing the consumer group of the connection. When you connect using a service, Autonomous Database performs more actions to configure the connection than just setting its consumer group.