The following restrictions are enforced on parallel direct path loads:
Neither local nor global indexes can be maintained by the load.
Rows can only be appended. REPLACE, TRUNCATE, and INSERT cannot be used (this is due to the individual loads not being coordinated). If you must truncate a table before a parallel load, then you must do it manually.
Additionally, the following objects must be disabled on parallel direct path loads. You do not have to take any action to disable them. SQL*Loader disables them before the load begins and re-enables them after the load completes:
Referential integrity constraints
Triggers
CHECK constraints, unless the ENABLE_CHECK_CONSTRAINTS control file option is used
If a parallel direct path load is being applied to a single partition, then you should partition the data first (otherwise, the overhead of record rejection due to a partition mismatch slows down the load).