All integrity constraints are enforced during direct path loads, although not necessarily at the same time. NOT NULL constraints are enforced during the load. Records that fail these constraints are rejected.
UNIQUE constraints are enforced both during and after the load. A record that violates a UNIQUE constraint is not rejected (the record is not available in memory when the constraint violation is detected).
Integrity constraints that depend on other rows or tables, such as referential constraints, are disabled before the direct path load and must be reenabled afterwards. If REENABLE is specified, then SQL*Loader can reenable them automatically at the end of the load. When the constraints are reenabled, the entire table is checked. Any rows that fail this check are reported in the specified error log. See "Direct Path Loads_ Integrity Constraints_ and Triggers".