Oracle Database Discussions

Hi,

Oracle Version : 10.2.0.3
Operating System : linux

Here i want to get the size of a table which consists of BLOB data type. I am able to get the normal table size with the below query.

select
   segment_name           table_name,   
   sum(bytes)/(1024*1024) table_size_meg
from  
   user_extents
where 
   segment_type='TABLE'
and   
   segment_name = 'MYTAB'
group  segment_name;

Why i am asking is when i take data pump backup for the Blob table it is showing around 8.5 GB.But when i use the same query for the BLOB data type tables is not show the 8.5 GB it is showing some thing around 4 MB.

Please help me how to calculate the size of the table with BLOB data type.

Thanks & Regards,
Poorna Prasad.S