The figure in sut81019.gif shows how data extraction differs between conventional path Export and direct path Export.
Conventional path Export uses the SQL SELECT statement to extract data from tables. Data is read from disk into a buffer cache, and rows are transferred to the evaluating buffer. The data, after passing expression evaluation, is transferred to the Export client, which then writes the data into the export file.
Direct path Export reads data from disk into the buffer cache and rows are transferred directly to the Export client. The evaluating buffer is bypassed. The data is transferred to the Export client, which then writes the data into the export file.