A direct path load is faster than the conventional path for the following reasons:
Partial blocks are not used, so no reads are needed to find them, and fewer writes are performed.
SQL*Loader need not execute any SQL INSERT statements; therefore, the processing load on the Oracle database is reduced.
A direct path load calls on Oracle to lock tables and indexes at the start of the load and releases them when the load is finished. A conventional path load calls Oracle once for each array of rows to process a SQL INSERT statement.
A direct path load uses multiblock asynchronous I/O for writes to the database files.
During a direct path load, processes perform their own write I/O, instead of using Oracle's buffer cache. This minimizes contention with other Oracle users.
The sorted indexes option available during direct path loads enables you to presort data using high-performance sort routines that are native to your system or installation.
When a table to be loaded is empty, the presorting option eliminates the sort and merge phases of index-building. The index is filled in as data arrives.
Protection against instance failure does not require redo log file entries during direct path loads. Therefore, no time is required to log the load when:
The Oracle database has the SQL NOARCHIVELOG parameter enabled
The SQL*Loader UNRECOVERABLE clause is enabled
The object being loaded has the SQL NOLOGGING parameter set