Oracle ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired

The Oracle error ORA-00054 can be solved by executing as DBA the following query

 select p.spid,s.sid,s.serial#,s.username,s.status,s.last_call_et,        p.program,p.terminal,logon_time,module,s.osuser  from         V$process p,V$session s  where         s.paddr = p.addr and s.status = 'ACTIVE' and         s.username not like '%SYS%';

This will return the PID of the hanging process

You can then SSH to the server ruining oracle and kill the process

 kill -9 PID