The most performant way to load data from an external table that will also guarantee direct path loading is:

The most performant way to load data from an external table that will also guarantee direct path
loading is:

A.
Using Create Table as Select (CTAS)

B.
Using Data Pump

C.
Using Insert as Select (IAS)

D.
Using transparent gateways

Explanation:

CTAS refers to a CREATE TABLE AS statement – a new table is created and populated with row
from a specified query.
The most common uses of CTAS are in these scenarios:
* Creating a table identical to another table in structure, but with a filter criteria applied to its data.
* Creating a table with small structural differences from an existing table.
For best performance use Direct Path Load. The conventional path uses standard insert
statements whereas the direct path loader loads directly into the Oracle data files and creates
blocks in Oracle database block format.
During direct-path INSERT operations, the database appends the inserted data after existing data
in the table. Data is written directly into datafiles, bypassing the buffer cache. Free space in the
existing data is not reused, and referential integrity constraints are ignored. These procedures
combined can enhance performance.
Reference: Oracle Database Administrator’s Guide 11g Release 1 (11.1), Loading Tables
http://www.filibeto.org/sun/lib/nonsun/oracle/11.1.0.6.0/B28359_01/server.111/b28310/tables004.h
tm