SQL *Loader : Direct Load : Description

With the conventional path load method, arrays of rows are inserted with standard sql INSERT statements, integrity constraints and insert triggers are automatically applied. But when you load data with the direct path, SQL*Loader disables some integrity constraints and all database triggers. The constraints that remain in force are:
* NOT NULL
* UNIQUE
* PRIMARY KEY (unique-constraints on not-null columns)
and the following constraints are automatically disabled by default:
* CHECK constraints
* Referential constraints (FOREIGN KEY)