lists all of the parallel operations that are possible on tables that are involved in referential integrity constraints. Table 21-1 Referential Integrity Restrictions

DML Statement	Issued on Parent	Issued on Child	Self-Referential
INSERT	(Not applicable)	Not parallelized	Not parallelized
MERGE	(Not applicable)	Not parallelized	Not parallelized
UPDATE No Action	Supported	Supported	Not parallelized
DELETE No Action	Supported	Supported	Not parallelized
DELETE Cascade	Not parallelized	(Not applicable)	Not parallelized

Delete Cascade

Delete on tables having a foreign key with delete cascade is not parallelized because parallel execution servers will try to delete rows from multiple partitions (parent and child tables).

Self-Referential Integrity

DML on tables with self-referential integrity constraints is not parallelized if the referenced keys (primary keys) are involved. For DML on all other columns, parallelism is possible.

Deferrable Integrity Constraints

If any deferrable constraints apply to the table being operated on, the DML operation will not be parallelized.

Trigger Restrictions

A DML operation will not be parallelized if the affected tables contain enabled triggers that may get fired as a result of the statement. This implies that DML statements on tables that are being replicated will not be parallelized.

Relevant triggers must be disabled in order to parallelize DML on the table. Note that, if you enable or disable triggers, the dependent shared cursors are invalidated.

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parallel dml & referential integrity constraints

Trigger Restrictions

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