Difference between user_segments and dba_segments

[tmgsam]

Hi Team,

SQL> select sum(bytes) from dba_segments where segment_type='TABLE';

SUM(BYTES)
----------
4.8594E+11

SQL> select sum(bytes) from user_segments where segment_type='TABLE';

SUM(BYTES)
----------
1453907968

SQL>

Waht is the difference between above queries.why there is difference in byets for both queries.Please help...