What is the functional difference between:
- importing a direct export dump (i.e. direct=y while exporting) and
- importing a conventional export dump (i.e. direct=n while exporting)
There is no difference. The choice you make on export effects how the export extracts data to the dump file... it does not have anything to do with importing.When you use DIRECT=Y this causes export to extract data by reading the data directly, bypassing the SQL Command Processing layer. This method can be much faster than a conventional 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.
In a direct path export, data is read from disk into the buffer cache and rows are transferred directly to the export client. The evaluating buffer is bypassed. The data is already in the format that export expects, thus avoiding unnecessary data conversion. The data is transferred to the export client, which then writes the data into the export file.
For More Information
- Dozens more answers to tough Oracle questions from Karen Morton are available.
- The Best Oracle Web Links: tips, tutorials, scripts, and more.
- Have an Oracle or SQL tip to offer your fellow DBAs and developers? The best tips submitted will receive a cool prize. Submit your tip today!
- Ask your technical Oracle and SQL questions -- or help out your peers by answering them -- in our live discussion forums.
- Ask the Experts yourself: Our SQL, database design, Oracle, SQL Server, DB2, metadata, object-oriented and data warehousing gurus are waiting to answer your toughest questions.