Find out which objects are locked using the following query:
select
substr(a.os_user_name,1,15) "OS User",
substr(a.oracle_username,1,8) "DB User",
substr(b.owner,1,8) "Schema",
substr(b.object_name,1,20) "Object Name",
substr(b.object_type,1,10) "Type",
substr(c.segment_name,1,15) "RBS",
substr(d.used_urec,1,12) "# of Records",
e.sid,
e.serial#
from v$locked_object a,
dba_objects b,
dba_rollback_segs c,
v$transaction d,
v$session e
where
a.object_id = b.object_id
and
a.xidusn = c.segment_id
and
a.xidusn = d.xidusn
and
a.xidslot = d.xidslot
and
d.addr = e.taddr;