Hey Nando Dessena,
Thanks a lot, the problem was with unicode.

Okai, Now i'm really in trouble.
This insertion process is getting over my head now.

First i tried simple insertion, it was obviously too too slow.
Then i used prepared statements, things started getting little bit faster.
Then again i used prepared statements with
Transaction.CommitRetaining() and it was beneficial too..

Than i heard about EXTERNAL TABLE and EXTERNAL Files.
Searched whole day about it, made it work and implemented it.
First i dumped my stuffs in a text file. Then i made table using this
file as EXTERNAL File.
Then i dumped it from that table to my desired table (i removed index
from table while dumping it and then recreated index.)
Now the problems were:
1. When i dump my things into text files. It requires hugh space.
Nevermind i can manage space. But since all the data type have to be
converted to CHAR types to store into EXTERNAL TABLE so i have to
convert all my types into fixed length CHARs and then attach to
external tables.
Now after i created the external table,
i queried the table like select col1,col2 from ext_table
while(reader.read())
{
(a) getvalues
(b) typecast it
(c) insert into my real table.
}
But this whole process is taking much time than expected.
Dumping to file happens to be fast. But dumping from external table to
my database table is very slow.
2. Also deleting and recreating index consumes time.

Can anyone please suggest me any thing...
I'd heard "EXTERNAL TABLES are the fastest way you can insert" but its
behaving slow.
I must have missed something..
I am in real need of some advice from you people...
Thanks in advance...