Oracle 12cR2: Controlling the Degree of Parallelism of Queries

Oracle Database 12.2 introduces a new instance parameter to control the Degree of Parallelism of queries, which involves a containers() construct.

By default, a query involving a containers() construct uses a DOP that is equal to the following value:

• In the case of a query in the CDB root, the value is (1 + number of open PDBs).

• In the case of a query in an application root, the value is (1 + number of open application PDBs).

  If the value of this parameter is less than 65535, the value is used as the DOP for all queries involving containers():

• In the session if the value was set at the session level

• In the instance if the value was set at the system level