If you get this error message when trying to alter or drop table or modify data in a table:
ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired
You can try running this sql/pl commands in sqlplus:
1. Check who locked the table:
select object_name, s.sid, s.serial#, p.spid
from v$locked_object l, dba_objects o, v$session s, v$process p
where l.object_id = o.object_id and l.session_id = s.sid and s.paddr = p.addr;
2. Remove the locks:
For each row of previous command’s output run following command:
alter system kill session 'sid,serial#';