If you want to figure out which sql statement is running by the active user in database:
select v.sid,
v.username,
v.machine,
v.server,
v.osuser,
v.process,
s.optimizer_mode,
s.hash_value,
s.address,
s.cpu_time,
s.elapsed_time,
s.sql_text
from v$sqlarea s, v$session v
where v.sql_hash_value = s.hash_value
and v.sql_address = s.address
and v.username is not null;
If you want to check sql statement for particular user:
select v.sid,
v.username,
v.machine,
v.server,
v.osuser,
v.process,
s.optimizer_mode,
s.hash_value,
s.address,
s.cpu_time,
s.elapsed_time,
s.sql_text
from v$sqlarea s, v$session v
where v.sql_hash_value = s.hash_value
and v.sql_address = s.address
and v.username='SCOTT';