1.select a.name,b.status from v$rollname a,v$rollstat b
where a.name in
(select segment_name from dba_segments where tablespace_name='UNDOTBS1')and a.usn=b.usn;
2. select s.username,t.xidusn,t.ubafil,t.ubablk,t.used_ublk
from v$session s,v$transaction t
where s.saddr=t.ses_addr;
3.select a.tablespace_name, a.file_id, a.block_id, a.blocks,
b.block_id
from dba_free_space a, dba_free_space b where a.tablespace_name = 'USERS'
and b.tablespace_name = 'USERS'
and a.tablespace_name = b.tablespace_name
and a.file_id = b.file_id
and a.block_id+a.blocks = b.block_id
4.