agasimani: Yes, agree with you. I think SQL Loader should be the most efficient way for loading the data. However I need to manipulate the records when importing, like add some more columns for each record. Can SQL Loader do this? Thanks!

kgb: You are really patient! There is a artical http://home.clara.net/dwotton/dba/java_insert.htm said turn off the auto-commit will improve the speed 10 times. But it seems it didn't work well to me. Hope it helps you. Thanks!

dbasupuser: Thanks! I will explore it. But can you tell some more about how to use the external table? Thanks!

Any more advice??? And how can I check if my oracle server is efficient or not? What are the important parameter for it? Thanks very much!