ALTER SESSION ENABLE PARALLEL DML;
To enable parallel DML mode in a specific SQL statement, include the
ENABLE_PARALLEL_DML SQL hint. For example:
INSERT /*+ ENABLE_PARALLEL_DML */ …
This mode is required because parallel DML and serial DML have different locking, transaction, and disk space requirements and parallel DML is disabled for a session by default.
When parallel DML is disabled, no DML is executed in parallel even if the
PARALLEL hint is used.
When parallel DML is enabled in a session, all DML statements in this session are considered for parallel execution. When parallel DML is enabled in a SQL statement with the
ENABLE_PARALLEL_DML hint, only that specific statement is considered for parallel execution. However, even if parallel DML is enabled, the DML operation may still execute serially if there are no parallel hints or no tables with a parallel attribute or if restrictions on parallel operations are violated.
DML mode does not influence the parallelism of
SELECT statements, DDL statements, and the query portions of DML statements. If this mode is not set, the DML operation is not parallelized, but scans or join operations within the DML statement may still be parallelized.
When the parallel DML mode has been enabled for a session, you can disable the mode for a specific SQL statement with the
DISABLE_PARALLEL_DML SQL hint.