You are using flat files as the data source for one of your data warehousing applications. To optimize the application performance, you plan to move the data from the flat files to clustered tables…

External table population creates a read-only Oracle view over a flat file and is not a direct loading mechanism into clustered tables; it requires additional INSERT steps and is not purpose-built for controlled bulk loads.

Oracle Data Pump operates on Oracle's proprietary binary format and is designed for database-to-database migration, not for ingesting raw flat file data sources.

SQL*Loader's conventional path load uses standard INSERT operations routed through the buffer cache and fully supports clustered tables, unlike the direct path method which bypasses the buffer cache and cannot write to clusters. Because the direct path restriction makes conventional path the only SQL*Loader option for clusters, it is the purpose-built, minimally invasive choice for migrating flat file data into this table structure.

INSERT INTO...SELECT requires the source to already be an Oracle-accessible object such as a table or view and cannot natively read from flat files without first defining an external table over them.